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1. Step 2 Size the PV Output and Inverter Input circuit conductors and ground wire EGC Check here if using a combiner box Most small PV systems of 3 strings or less don t use a combiner box Where there are lots of separate strings and therefore parallel wire combinations of positive and negative a combiner box is used to reduce all the positives to one beefier wire and all the negatives to one beefier wire 19 Number of Array Strings This is the number of module groups connected in series for instance 2 strings of 10 modules or 3 strings of 7 modules String size is selected to achieve a specific voltage in the PV output circuit and usually divides equally into the number of strings For example a count of 20 modules divides equally into two strings but not three Inches between conduit amp roof Conduit run across a roof should never sit directly on it That s because it gets too hot A typical range is 3 to 6 inches Check here if no conduit on roof In most residential systems the wire leaving a roof based junction or combiner box must travel through conduit Enter Wire Type In most cases the type used is THWN 2 which is water resistant and rated at 90 degrees Celsius For more on selecting wire read this intro Project Name Optional field Use the homeowner s name address or other unique identifier Step 3 Size the Inverter Output conductors and ground wire EGC Inverter AC Output Imax T2. out of range Otherwise the box will read OK NOTE When matching an inverter to an array always take the extra step of using the inverter manufacturer s sizing tool to verify the results TheSolarPlanner com Modules Inverter and String Sizing Worksheet is designed to supplement these tools not replace them Click the Resources tab on the worksheet to access manufacturer sizing tool links Extra Pages Resources Includes links to product pages in order to research module and inverter specs online inverter sizing tools and tutorials There is also a Celsius Fahrenheit Temperature Conversion Table 8 WIRE SIZING WORKSHEET Purpose of this Worksheet After selecting your modules inverter and array string sizes and measuring wire distances between your array and the home s main service panel you Il have the information you need to size your circuit breakers and wire This form crunches the data using rules laid out by the NEC therefore providing the numbers and specs needed when preparing a building permit application After the data entry and calculations are complete a printable report is also generated You can use the report to order wire and as an installation guide Limitations This worksheet is limited to home grid tied PV systems under 10k that use one central inverter either with or without a transformer and standard DC photovoltaic modules The form cannot be used if the circuit includes
3. 100 for Cost Analysis worksheet 200 for Wire Sizing Contact Rosemary Regello at rregello thecityedition com for more information 2 General Instructions Purpose of TheSolarPlanner com Worksheets These forms will help you plan finance design or configure a residential grid tied PV system using one central inverter sized between 2 000 and 10 000 AC watts i e 2k to 10k without battery back up No battery or charge controller sizing is included The worksheets are ideal for trying out different system sizes array orientations tilts or other options to get the most efficient and cost effective combination of variables You can easily type over existing data and generate different calculations to see what array size or equipment choices work best The forms are also designed to print out on 8 5 X 11 inch paper You may need to adjust the print breaks with Excel s Page Set up function Using MS Excel You don t need to know much about Excel to use these worksheets The data entry and other features are similar to online and other computerized forms Each Excel file is called a workbook and is divided into one or more worksheets and other pages At the bottom of the first page you ll see several file tabs By clicking on these you can navigate around the workbook Typically a workbook contains three tabs Intro Worksheet and Resources Saving downloaded files When you first retrieve a worksheet from TheSolarPlanner com
4. Calculation to the ranges laid out in NEC Table 310 15 B 16 formerly Table 310 16 Maximum Ampacities for conductors inside conduit The corresponding gauge from this table will appear in the cell Note The minimum gauge for this formula is 12 the maximum is 3 Steps 3 Size Inverter Output Conductors Indoor Temperature Correction Compares value in the Highest Indoor Temp box to the ranges laid out in NEC Table 310 15 B 2 Ambient Temperature Correction Factor and returns the corresponding result If no value is entered for Highest Indoor Temp this cell returns a value of 1 Conduit Adjustment If the box Conduit will carry more than 3 conductors is checked this cell returns a value of 80 Otherwise it returns a value of 100 Ampacity Calculation If the box for Inverter will be indoors is checked the formula for this cell is Imax 1 25 Indoor Temp Correction Conduit Adjustment If the box is not checked the formula is Imax 1 25 Temp Correction Factor from Step 1 Conduit Adjustment Minimum Wire Gauge for Conductors Compares the amount in Ampacity Calculation to the ranges laid out in NEC Table 310 15 B 16 formerly Table 310 16 Maximum Ampacities for conductors inside conduit The corresponding gauge from this table will appear in the cell Note The minimum gauge for this formula is 12 the maximum is 2 Steps 4 Measure Wire Lengths Wire Lengt
5. to change watts into kilowatts This total is then multiplied by Cents per KWH rate and 365 days Kilowatt Hours Saved Multiplies Watts by Less Hours ON and STANDY then divides the total by 1000 to change watts into kilowatts The result is multiplied by 365 days Annual Savings Multiplies Kilowatt Hours Saved by Cents per kWH rate Totals This Page Only This row at the end of the first page sums the data in the respective columns Totals Cumulative This column at the end of the second page combines the first page and second page column totals Extra Pages Resources links to other energy audit calculators forms and tools 3 UTILITY BILL AUDIT Purpose of this Workbook The Utility Bill Rates worksheet allows you to determine how many kilowatt hours kWh of electricity a home uses in one year as well as the cost This information is the starting point for designing a photovoltaic system A system should ideally produce 100 of the killowatt hours needed to offset electricity that comes from the utility grid The energy bill audit is also needed to calculate payback time on a home solar power investment Limitations Designed for a U S residence that receives electricity from a utility grid Data Requested From the homeowner s last available 12 monthly electricity bills the following information for each month is needed Rates This is the price per kilowatt hour kWh and is usu
6. local utility company and any other authority having jurisdiction AHJ The National Electric Code and local fire regulations also apply to home PV installations whether grid tied or off grid standalone systems These worksheets are designed to function independently of each other However it s a good idea to complete at least some of them in the order that they re listed since the values calculated on one form will be requested on the next You cannot alter any formulas or labels on the worksheets because they are protected by an Excel developer function This means you can only enter data in the blank i e white boxes of a form There are a few default values inserted in some white boxes as a convenience but you can always change these numbers If a calculation does not produce a satisfactory or any result be sure to check for any previous data cells not filled in mistyped entries wrong units used e g inches vs feet or multiple check boxes selected Read the form specific instructions for help in troubleshooting any difficulty If you find any design errors in these worksheets or experience compatibility issues or printing problems please let us know info thesolarplanner com Services Available Form customizing consulting technical writing and business support are available from TheSolarPlanner com at a starting rate of 25 per hour You can also get a worksheet unlocked and modify it yourself for 50
7. microinverters string inverters or battery backup A maximum of six array strings can be configured The available wire gauge range is AWG 2 TO 12 and only 90 degree rated wire may be used It is assumes that electricity on the array side of the inverter is DC high voltage up to 600 volts and AC split phase 240 volts 120V AC through two hot wires between the inverter and main service panel 18 Data Requested Step 1 Size the source circuit conductors and ground wire Max High Temperature This is for your local geographical area and must be entered asa Celsius value only You can click on the Solar ABC s link to retrieve this number online Most PV designers use what s called the 2 avg high temp developed by the professional trade association ASHRAE Module Brand and Model and Inverter Model This info comes from the manufacturers Module Ise Short circuit current Module Ipm Operating current Note You ll find these values and other relevant data on the module s spec sheet If you Click on the Resources tab of this workbook several links are provided to help you search Check box if system is positive grounded Most circuits are negative grounded which means the negative wire running from the array is the grounded conductor However on occasion a positive grounded circuit and inverter are used instead If the box is checked this simply triggers a note on the Report and does not affect any calculations
8. store your original downloaded worksheets in a folder called Originals Then before starting work on any worksheet save the original under a different name and store it in a different folder or on your desktop To type over and replace existing data simply move your cursor to the cell box and start typing To correct part of the data in a cell without replacing all of its contents double click on the cell first Make your changes then press Enter If you change your mind and decide not to change data while your cursor is still inside a cell press ESC to keep the existing data If you finish changing data and exit the cell but then want to change it back to its original data go to the Edit Menu at the top and select the Undo function You cannot type in any shaded areas gray blue yellow or green or change labels rows or columns on a worksheet However you should be able to create new worksheets within a workbook As stated earlier to unlock or unprotect a worksheet you must contact the worksheet developer See Services Available on Page 2 for contact info Sometimes your data is not accepted in a cell due to data validation rules When this happens an error message will appear explaining the parameters or limits of the data that you can enter For instance you re asked to enter a Celsius temperature and you type in Fahrenheit degrees by mistake An error message will appear if the value is
9. tallied in the calculations If the box is checked the home run length is tallied in the PV Output Circuit Positive Wire field and the near end run is tallied in the Negative Wire field If the box isn t check the home run is tallied in the Negative Wire field and the near end run in the Positive Wire field Distance feet between junction box combiner and the inverter PV Output Circuit This distance applies to the gap between the two electrical components You must first determine the wire s physical path through conduit then measure the length from point to point along the way Do not enter a roundtrip distance Distance of EGC if different from conductors PV Output Circuit Skip this field If the ground wire will travel the same route as the conductors Wire distance between inverter and main service panel Inverter Output Circuit This distance applies to the gap between the two devices mentioned You must first determine the wire s physical path through conduit then measure the length from point to point along the way Enter the sum of distances No roundtrip Distance of inverter EGC if different Inverter Output Circuit Skip this field If the ground wire will travel the same route as the conductors Step 5 Perform voltage drop calculations Module Operating Volts Vpm This is the operating or power max voltage listed on the module spec sheet Module Cable Length in inches This length is listed on th
10. the number of minutes by 60 e g 15 60 0 25 Note Excel provides a manual calculator that be retrieved by going to the Tools menu and selecting calculator Appliances Replaced List any major appliances electronics or other loads in the home that will be replaced with energy savings models Data must be supplied for the following fields Old Size watts the size of the incandescent bulb s you re replacing New Size watts If you haven t bought the replacement bulbs yet use the yellow conversion chart to pick a CFL wattage size Hourly usage daily Estimate how many hours the appliance uses in a day Some appliance usage requires a bit of calculating For example a washing machine that runs twice a week for an hour each time would produce an equation like this 2 hours divided by 7 days which equals 0 286 hours daily For some appliances that operate automatically throughout the day this data should be based on the duty cycle of the machine listed on its spec sheet For instance a refrigerator may have a 50 duty cycle which means it s operating half the time To convert this percentage into daily hours multiply it by 24 e g 0 50 X 24 equals 12 hours Calculations Lights Total Sum of the Quantity Column Annual kWh Saved Lights Subtracts New Watt Size from Old Watt Size then multiplies the difference by Quantity and 365 The result is then divided by 1 000 to chang
11. type Distance of home run from array far end to junction combiner box A home run is a length of wire that connects the far end of each array string of modules with the junction or combiner box This distance in feet applies to Strings 1 4 You don t need to multiply the length by the quantity of strings Distance of near end run to box Ifa module cable is attached directly to the junction or combiner box you can skip or enter zero in this data field However if the distance between the first module and the box is longer than the length of the module lead you Il need to add a wire extension If that s the case enter it here String 1 2 3 4 The worksheet can accommodate input wire lengths for up to four sets of wire positive and negative running from the array to the junction or combiner box 20 Check box if home run is positive wire It s up to the designer whether the positive wire or negative wire will exit the far side of the box Because it s on the far side and has a longer run than the other wire this is known as a home run Length for Ground Wire EGC Source Circuit This length depends on whether you plan to use jumper clips to ground the array or run a traditional ground wire along each row of modules If clips are used the EGC must simply connect one row to the next then run to the junction box Check box if home run is positive wire This field affects how the wire lengths are
12. website it may open inside your internet browser Do not work on it however until you ve saved the file in your version of Excel exited the browser and then reopened the document in your software Follow the instructions on the Intro page of the new workbook To download another worksheet use the back arrow on your internet browser to access the worksheets menu page A word about macros No macros are used in any worksheet from TheSolarPlanner com A macro is a set of commands transmitted via a programming language On rare occasions macros have been used by hackers as a vehicle for spreading viruses For that reason whenever you open an Excel workbook if any macros are included yov ll be asked if you want to enable or disable them If you re not expecting a macro or are not sure of the source of the document you should always select Disable Of course since no macros are used by TheSolarPlanner com you should never be asked If you are asked select disable then close the document and delete it from your computer Always download worksheets directly from TheSolarPlanner com website Excel help continued on next page Data Entry To move around a worksheet use the arrow and tab keys After typing in data press Enter Boxes to be completed by the user are white and framed by a thick black line Shaded boxes containing labels or Excel values should be locked preventing any data entry It s recommended that you
13. EL Data Sets aka Redbook or by using a calculator available on many websites PV Watts also provides this data However a more reliable number can be determined from an array site assessment using a Solar Pathfinder Solmetric Sun Eye or other shading analysis device Other variables that contribute to the amount of daily insolation over an array are the azimuth orientation ideally a direction facing near or due south the angle of the roof or tilt angle of the modules and the latitude of your city You ll find more help on this subject by clicking on the Resources tab Derate Factor This factor reduces the amount of array watt production based on wire losses projected system downtime module age soiling of the array and other common occurrences PV Watts provides a calculator to help you hone in on exact number A default of 77 is provided For help determining the right value you ll find a link in the worksheet to the online derate calculator provided by the National Renewable Energy Laboratory NREL When using this or another tally please note that the numbers are expressed in percentages If for example you don t want any derate for a certain item like the inverter efficiency rating or shading you would enter either 100 or 1 depending on whether the percentage is expressed with or without decimals Grid Offset The term offset refers to the amount of utility provided electricity a homeown
14. Module Brand For example Sanyo or Sharp Model Usually a combination of letters and numbers STC Standard Test Conditions This is the factory tested operating wattage of the module It s also referred to as the nameplate wattage Operating Current Ipm Amperage under which the module usually operates Short Circuit Current Isc This value is used for calculations that compae the sum of currents in parallel to the maximum current in the inverter can handle Negative Power Tolerance This multiplier is used to provide a lower limit on the operating STC wattage based on the factory measured performance of solar cells used in the construction of the module The manufacturer guarantees the power will not be lower than this amount When possible choose a module that has a very low or no negative power tolerance Use a decimal e g 05 to enter this value DO NOT use the negative symbol Power Max Voltage Vpm This is the voltage that an inverter s MPPT circuit will try to maintain in the module whenever the system is operating Open Circuit Voltage Voc This voltage is used for calculations concerning the maximum possible voltage in a PV circuit Voltage Temperature Coefficient Voc A coefficient is a multiplier This one is used in conjunction with Voc to calculate the maximum possible voltage in a PV circuit Be sure to include negative symbol in the data field
15. Power Temperature Coefficient Pmax This coefficient is used in conjunction with the Power Max Voltage to calculate the lowest possible temperature in a PV output circuit You would normally use the Voltage Maximum Power Vmp Coefficient but the latter spec is often not listed on a module spec sheet If it is you can use it instead of the Pmax Coefficient Be sure to include negative symbol in the data field Module Operating Temperature Range Low High These range temps should be located in the miscellaneous section of a module spec sheet Be sure to use Celsius for all temps and include the negative symbol if it s listed Inverter Specs The following data fields pertain to a specific inverter that s being 16 considered in a PV array To complete the fields youll need to download the product literature and or spec sheet This material is typically available on the websites of online suppliers and inverter manufacturers Inverter Brand For example SMA or Fronius Model Different manufacturers use different naming conventions The field allows you to type in long name but it may not show the entire name in the box AC Watts This the wattage that the inverter sends to the main panel which is not always the same as the PV watts it receives from the array Input Voltage Max Min OR Range Low High If you find a Startup Voltage spec use that as the low and if there s a Max DC
16. Sizing Worksheets Version 1 Free Last update 1 12 2014 Aspen Skiing Co NREL Contents Disclaimer and Important Info Page 2 Services Available Page 2 General Instructions Please Read Page 3 Specific Worksheets How the Instructions are Presented Page 5 1 Energy Savings Measures Page 6 2 Appliance and Load Analysis Page 8 3 Utility Bill Audit Page 9 4 Array Sizing Page 10 5 Tilted Array Sizing Page 12 6 Cost Payback Profit Analysis Page 14 7 Modules Inverter and String Sizing Page 15 8 Wire Sizing Page 19 Note Sample completed forms are available at TheSolarPlanner com Copyright 2013 2014 TheSolarPlanner com All rights reserved iG OS DISCLAIMER AND IMPORTANT INFO Keep the following points in mind when using the free home photovoltaic system sizing forms provided by TheSolarPlanner com As with all calculators software and other tools these worksheets do not guarantee success in selecting or configuring the right PV system It s solely the user s responsibility to decide on a contractor and system package a design and or installation plan No guarantees are made about the accuracy or reliability of the worksheets TheSolarPlanner com strongly advises homeowners to secure the services of a licensed solar installer when planning and installing a PV system In most places a building permit is required before any work can begin along with approval from the
17. Voltage listed use that as the high Otherwise use the figures provided in the low high range Maximum Array DC Current This refers to input current listed in the inverter specs Operating Temperature Range Low High These range temps should be located in the miscellaneous section of a inverter spec sheet Be sure to use Celsius for all temps and include the negative symbol for a low temp if needed Maximum DC Watts This spec may be given as part of a range that applies to the input watts from the array Use the higher figure in that case Efficiency Rating The default is 95 This is the percentage of watts that will be delivered to the main service panel and or net meter Most inverters operate at around 95 efficiency The other 5 is used to power the inverter itself or otherwise gets dissipated as heat If inverter efficiency was included in your derate factor calculations back in the array sizing step you should either enter 100 on this form for the Efficiency Rating or go back and adjust the value for the derate factor on your Array Sizing Worksheet In the latter case the value for Array Watts Needed on the current worksheet should change as a result Start up Voltage Adder The default is 0 Start Up Voltage is the voltage necessary to start the inverter in the morning or early afternoon when the sun starts shining on the array or if the inverter has shut off due to a power outage or
18. alculated in Step 4 Conductor Gauge This value was calculated in Step 2 Ohms per Kilofoot Looks up Conductor Gauge in NEC Chapter 9 Table 8 and returns the corresponding value Note The table s value for stranded wire rather than solid is used in all cases Inverter Output Circuit Voltage Drop Variables AC Maximum Current This cell repeats the Inverter AC Output Current Imax value entered in Step 3 Wire Length The formula adds the Inverter Output Positive and Negative wire length values calculated in Step 4 25 Conductor Gauge This value was calculated in Step 3 Ohms per Kilofoot Looks up Conductor Gauge in NEC Chapter 9 Table 9 and returns the corresponding value Note The table s value for stranded wire rather than solid is used in all cases Voltage Drop Calculations Source Circuit Voltage Drop The formula for this cell is the Operating Current Length 1000 Ohms per Kilofoot The answer is expressed in volts Circuit Volts The formula is Module Operating Voltage Vmax Module Count Array Strings Percentage Divides Voltage Drop by Circuit Volts then multiplies the result by 100 PV Output Circuit Voltage Drop The formula for this cell is the Operating Current Length 1000 Ohms per Kilofoot The answer is expressed in volts Circuit Volts Repeats the value from Source Circuit Circuit Volts Percentage Divides Voltage Drop by Circuit Volts then multiplie
19. alculator to help you hone in on exact number A default of 77 is provided See Array Sizing worksheet above for more on derates Grid Offset The term offset refers to the amount of utility provided electricity a homeowner wishes to replace by installing a solar electric system It s expressed in the form of a percentage For example if a customer uses 10 000 kilowatt hours annually and would like to replace or offset about a third of it with PV power then he or she would need an array that generates 3 333 kWh A default value is 50 is provided See Array Sizing worksheet for more on Grid Offset Array Dimensions Enter the length of width of each array location measure on the roof or ground When measuring keep in mind that a roof array must leave a few feet on the top and sides for a fire walkway and or maintenance worker access How much walkway must be set aside depends on the local fire and building codes Do not include walkway space in the dimensions Site s Latitude This is the latitude in relation to the Equator measured in degrees A variety of websites online offer help in calculating a latitude based on a zip code or city state entry Latitudes in the continental United States range from about 30 degrees in Florida to 50 degrees in the northern states The highest acceptable latitude for this worksheet is 50 degrees Array Tilt Angle Maximum You can experiment with different angles to see
20. ally divided into four or more rates Some utility companies use a tiered rate structure which provides a kWh quota per rate per month The first and cheapest is known as the baseline rate and is charged for the first several hundred kWh Once you exceed that threshold you re charged the next highest rate until its quota is reached and so on Rates continued Some companies have a time of use TOU system which divides rates into a morning early afternoon period late afternoon peak price period late night low rate period etc Whichever your rate structure pick the four rates for which you are charged through the course of 12 bills one year If you or the homeowner paid more than four rates for electricity you ll have to combine two or more rates into one column on the worksheet This means averaging the rates and then adding all the hours together Note You can ignore surcharge based kWh rates which are typically priced at a fraction of one cent and don t result in a substantial amount of money You should also ignore flat fees which are charged on the bill regardless of kilowatt hour usage These charges are not affected by kilowatt hour consumption Kilowatt Hours kWh Type in the monthly kWh hours in the corresponding column that lists the rate charged for those hours Calculations Total kWh for Month Sums the kWh values listed under the four rates for the month Monthy usage of bill D
21. cell will read check wire gauge Otherwise the cell will read YES If no O C Device is entered then this cell will read O C Device Required Step 7 Choose a Ground Wire and Gauge for Each Circuit Wire Type The boxes for PV Output and Inverter Output repeat the corresponding values you entered in Steps 2 and 3 If no value was entered then these cells will display a zero Note When using a transformerless inverter NEC Article 690 35 applies Since the PV system circuit is ungrounded you must use red black wires instead of black white Also both conductors must receive O C protection where fuses or breakers are installed For exposed wire i e not run in conduit only PV Wire can be used for the conductors Extra Pages This workbook includes the following documents that can be accessed by clicking on their file tabs at the bottom of the page Report Presents all the key wire selection Copyright 2013 2014 information extracted from the Wire Sizing TheSolarPlanner com worksheet on a single printable page This can be used for preparing a budget purchase order or building permit application NEC Tables Excerpts from the official NEC tables that apply to wire sizing focusing on the types and gauges of wire most commonly used in residential PV systems sized from 2 to 10 kilowatts There is also a Celsius Fahrenheit Temperature Conversion Table Resources Includes links to onl
22. ck the O C device rating in Step 6 and look it up in Table 250 122 which is shaded green to the right of the fill in boxes For example if you re using a 20 amp O C device the correct gauge for the EGC is 12 3 A transformerless inverter is used Under this scenario the NEC stipulates that the EGC in each circuit must be rated for twice the ampacity of the circuit regardless of overcurrent protection So you will look in Step 6 under the column Overcurrent Ampacity Calculation and multiply the value listed by two Next you will need to check the NEC wire ampacity tables which can be found by clicking on the file tab NEC Tables Find the table for free air conductors if you re working on the Source circuit For the PV Output and Inverter Output circuits use the table for conductors in conduit Pick the gauge whose ampacity is nearest to the result you calculated For example if the PV output circuit s O C ampacity is 25 10 A multiplying by two produces the result 50 20 Looking that up in the ampacity table for THWN 2 conductors in conduit the nearest acceptable gauge is AWG 8 lt a A z Susan Bilo NREL Wire Type This field is included because EGC for the source circuit is often not the same wire used for the conductors It s common and often recommended to use Bare Copper AWG 6 which is thick enough to be exposed on a roof without breaking In a home PV instal
23. e In the Source Circuit there is no conduit adjustment Source Circuit Is the Wire Ampacity equal to or greater than the O C Devicr Rating If there s a value in the corresponding O C Device Rating box this cell compares the value in 26 Derated Wire Ampacity to Overcurrent Ampacity Calculation If it s less then the cell will read check wire gauge Otherwise the cell will read YES If no O C Device is entered then this cell will check the number of Array Strings value in Step 2 to see if there are more than two strings If there are then this cell will read O C Device Required Note check wire gauge is not an error message but rather a guide for filling in the Final Minimum Gauges in the last part of Step 6 Be sure to read the form instruction that s typed in red PV Output Circuit Is the Wire Ampacity equal to or greater than the O C Device Rating If there s a value in the corresponding O C Device Rating box this cell compares the value in Derated Wire Ampacity to Overcurrent Ampacity Calculation If it s less then the cell will read check wire gauge Otherwise the cell will read YES Inverter Output Circuit Is the Wire Ampacity equal to or greater than the O C Device Rating If there s a value in the corresponding O C Device Rating box this cell compares the value in Derated Wire Ampacity to Overcurrent Ampacity Calculation If it s less then the
24. e module spec sheet and is included in wire distance calculations Module Count Enter the number modules in the PV array s Check box to use the next beefier wire gauge for this circuit You have the option of adding one gauge to the wire calculation of each circuit array PV output and Inverter output Generally if the voltage drop calculation returns a number much larger than 3 you should go with the next gauge Note You ll be able to adjust wire gauges again in the next step Steps 6 Compare wire gauge ampacities to any overcurrent device ratings Enter O C Rating if any O C stands for overcurrent and this column asks if you want to use a fuse or breaker i e an overcurrent deviceO in the circuit If you have more than two array strings an O C device is required in the Source Circuit The Inverter Output Circuit will always require a circuit breaker at the Main Service Panel so the last box must be filled in Overcurrent protection is optional for the PV Output Circuit To pick an O C rating which is its size in amps you can click the Resources tab and review the information and links provided Generally fuses are used in the Source and 21 PV Output circuits due to the high voltages In the Inverter Output Circuit a two pole backfed breaker is required at the Main Service Panel The sizing for this type of breaker is more limited e g 20 30 40 amps than other types of O C devices Note T
25. e watt hours to kilowatt hours Total Lights kWh Saved Sums the column of Annual kWh Saved Annual Utility Savings Lights Multiplies Annual kWh Saved Lights by Cents per kWh lt lt 4 GEA e ai 1AA Brothers Electric N Annual kWh Saved Appliances Subtracts New Watt Size from Old Watt Size then multiplies the difference by 365 The result is then divided by 1 000 to change watt hours to kilowatt hours Total Appliance kWh Saved Sums the column of Annual kWh Saved Appliances Utility Savings Appliances Multiplies Annual kWh Saved Appliances by Cents per kWh Combined Savings Sum of Annual Utility Savings Lights and Appliances Extra Pages Resources links to other energy audit calculators forms and tools 2 APPLIANCE AND LOAD ANALYSIS Purpose of this Workbook The Appliance Load Analysis worksheet may not be needed for sizing an array but some tax rebates require a more extensive energy audit than the previous worksheet provides This one allows you to tally all your household electrical devices weigh their impact on your kilowatt hour usage and if necessary takes steps to lower consumption In conjunction with the Energy Saving Measures worksheet this one can also help you lower consumption as part of a plan to accelerate payback on a PV system investment Note A load analysis is mandatory when designing a stand alone system not connected to the utilit
26. e worksheet calculation of total annual savings can be used in a cost and or payback analysis of the proposed or installed PV system Limitations Designed for an existing U S residence connected to the utility grid Data Requested Cents Per kWh Rate This is the baseline rate charged by the home s utility company It can be found on the monthly bill for electricity or the utility company s website page Light Bulbs Replaced Generally this section is used for incandescent bulbs replaced with compact fluorescent bulbs CFL s Incandescent bulbs burn 90 of their electricity as heat and only 10 as light That s why they re being phased out by order of the U S Government The worksheet provides a conversion chart to help you select or record the potential change in wattage Data must be supplied for the following fields Old Size watts Quantity In other words the number of bulbs of the same wattage New Size watts If you haven t bought the replacement bulbs yet use the yellow conversion chart to pick a CFL wattage size Hourly usage daily Estimate how many hours one bulb uses in a day If there is more than one bulb an average must be calculated For example if you use two 75 watt bulbs fours a day and three 75 watt bulbs 15 minutes a day then the average would be 2 X 4 3 X 25 5 which equals 1 75 hours each Be sure to convert minutes into hours by first dividing
27. er wishes to replace with solar It s expressed in the form of a percentage For example if a customer uses 10 000 kilowatt hours annually and would like to replace or offset about a third of it with PV power then he or she would need an array that generates 3 333 kWh A default value is 50 is provided In an ideal world most people would opt for a 100 offset However since the baseline rate charged by most utility companies is cheap under 15 cents per kWh it s not practical to buy a big solar system since at those rates it will take too long to achieve payback Rather customers are encouraged to buy a system sized to offset only the higher tiered rates That way the break even point is reached in about 7 years after which profit starts to accrue from avoided utility charges and continues on through the life of the system Hence a grid offset between 30 and 60 is quite common Array Dimensions Enter the length of width of each array location measure on the roof or ground When measuring keep in mind that a roof array must leave a few feet on the top and sides for a fire walkway and or maintenance worker access How much walkway must be set aside depends on the local fire and building codes Do not include walkway space in the dimensions Module Length and Width These dimensions depend on the brand and model of the module you re considering To browse the spec sheets of different products use the l
28. h Calculations Source Circuit Positive If the box Home Run is the positive wire is checked this cell returns the sum of values for Strings 1 4 entered on the Home Run line If the box is not checked it returns the sum of values for Strings 1 4 entered on the Near End Run line if any Source Circuit Negative If the box Home Run is the positive wire is checked this cell returns the sum of values for Strings 1 4 entered on the Near End Run line if any Otherwise it returns the sum of values for Strings 1 4 entered on the Home Run line 24 Source Circuit EGC Repeats value entered in Length for Ground Wire EGC for this circuit PV Output Circuit Positive Multiplies the value entered for Distance between the Junction Combiner Box and Inverter by Conductors Exiting the Box Step 2 divided by two PV Output Circuit Negative Repeats the value of PV Output Circuit Positive PV Output Circuit EGC If a value is entered in Length for Ground Wire EGC for this circuit this cell repeats it However if no value is entered then this cell repeats the value of PV Output Circuit Positive Inverter Output Circuit Hot Takes the value entered in Wire distance between Inverter and Main Panel and multiplies it by two Note there are two hot wires running from the inverter each carrying half of the component s 240 volts Inverter Output Circuit Neut
29. his is the operating current sometimes listed as Imp You ll find this value on the inverter spec sheet Note An output current higher than 16 amps usually means that the circuit breaker at the main panel must be at least 30 amps Panel bus bars rated at 100 125 amps cannot accommodate more than a 20 amp breaker without modification It s important to check with an electrician or solar company about this before choosing an inverter Check box if inverter will be outdoors The location of the inverter determines what ambient temperature to use Temperature affects ampacity of the wires and must be factored into any gauge calculation If indoors estimate highest temp in Celsius Default 35 This temp must be estimated based on the location e g unair conditioned garage and the summer high temp Check here if using a transformerless inverter In this scenario the usual grounded conductor is not grounded delivering slightly greater power output than a traditional inverter Consequently the ground wire ECG must have double the ampacity as the positive and negative per the National Electric Code When you check the box a note is triggered in Step 7 Sizing the Ground Wire and on the Report Enter Wire Type In most cases the type used is THWN 2 which is water resistant and rated at 90 degrees Celsius For more on selecting wire read this intro from Civic Solar Step 4 Determine how many feet you need for each wire
30. his worksheet only allows data input for one O C device per circuit Conductor Gauges In this section you re asked to furnish the final minimum conductor gauges for each of three circuits in the PV system These numbers will be used in the Wire Sizing Report The values you choose should be based both on the data in the third column in the table of this section called Conductor Gauge as well as on info provided in the fourth column Is the derated wire ampacity equal or greater than the O C Rating If an O C device is not used in the circuit or the fourth column box for this circuit reads Yes you can simply retype the gauge size listed in the table Otherwise refer to the instructions furnished on the form and printed in red If you are unsure about available O C device sizes click on the Resources tab for help Step 7 Choose a Ground Wire and Gauge for Each Circuit Minimum EGC Gauge This refers to the equipment grounding conductor aka ground wire in each of the three circuits Depending on the type of inverter chosen for the PV system and whether or not overcurrent protection is used in the circuit the result you enter into each box will be determined by one of three formulas 1 A normal inverter and no O C device in the circuit If this is the case use the same gauge wire you picked in Step 6 for the circuit conductors 2 A normal inverter and an O C device is used Here you ll che
31. ine wire sizing tools product pages in order to research module and inverter specs and online tutorials 27
32. inks provided on the Resources page of this workbook Note You might also consider using a landscape orientation instead of the usual portrait if this allows you to fit more modules into the array space To do this type your module s width into the worksheet s module length field and your module s length into the worksheet s module width field This will produce the correct calculations for a landscape scenario Default dimensions of 65 and 40 inches are provided for module length and width respectively Module Watt Size Enter the nameplate or STC wattage of the module brand and model you re considering For residential PV arrays the standard sizes are 185 235 240 and 250 Calculations Total Array DC Watts Needed Divides Annual Kilowatt Hours by Daily Peak Sun Hours X 365 then divides the result by the Derate Factor Rows Possible Divides Array Width by Module Length then reduces the result down to the nearest integer An integer is a 11 whole number This calculation also includes a one inch gap between rows by adding 5 to Module Length before the division If you need more space than that add it to the module dimension Note Each module only needs to hold half the extra spacing Quantity per Row Subtracts 3 5 inches from the Area Length then divides the result by the Module Width plus 0 5 inches The result is reduced down to the nearest integer The subtraction and additi
33. ivides Total kWh for Month by Annual kWh Total Annual kWh Total Sums the 12 values entered under Total kWh for Month Rate of Bill Divides the kilowatt hours for a certain rate by the total hours for the year to determine a percentage Some of the values highlighted in yellow will be requested on the Cost Payback Profit Analysis workbook For your convenience the Utility Bill Rates worksheet is included in the Cost workbook and can be accessed be selecting the designated file table 4 ARRAY SIZING WORKSHEET Purpose of this Worksheet The Array Sizing worksheet determines how many modules will fit inside the array space s measured during the site survey and the total watts the array will produce It also compares this energy production against the kilowatt hour usage of the homeowner and calculates the percentage of grid offset Limitations Designed for a residence that receives electricity from a utility grid Maximum annual kilowatt hour kWh usage must be under 14 000 Data Requested Annual Kilowatt Hour Usage This number is based on the Annual Kilowatt Hours determined on the Utility Bill Audit worksheet The highest value you can enter is 14000 The lowest is 1000 Daily Peak Sun Hours Sun hours factor into the calculation of how many kilowatt hours of electricity a solar array will generate each year This value can be an average retrieved by looking up your city s solar insolation data in the NR
34. lation Gauge 6 choice should also suffice for all three A Sa scenarios laid out above For the PV Output ee and Inverter Output circuits the wire type selected for the conductors in Steps 2 and 3 is automatically transferred into the data AstroPower NREL boxes Wire Sizing Calculations start on next page 22 Calculations for Wire Sizing Step 1 Size the source circuit conductors and ground wire Temperature Correction Factor Compares the Max High Temp to the ranges laid out in NEC Table 310 15 B 2 Ambient Temperature Correction Factor and returns the corresponding result Ampacity Calculation Multiplies the Module Isc by 1 56 and divides the result by the Temp Correction Factor Minimum Wire Gauge for Conductors Compares the Ampacity Calculation value to the ranges laid out in NEC Table 310 15 B 17 formerly Table 310 17 Maximum Conductor Ampacities in Free Air and returns the corresponding result Note The minimum gauge for this formula is 12 the maximum is 3 Step 2 Size the PV Output and Inverter Input circuit conductors and ground wire EGC Circuit Isc Checks to see if the cell indicating a combiner box is checked If it is then Module ISC is multiplied by Number of Array Strings If the box isn t checked the cell will show the Module Isc value from Step 1 Conductors Exiting Box If Combiner box check box is left empty divides the value entered in Array String
35. n t within the acceptable temp range You can click Retry to enter different data or select Cancel to leave the existing data if any in the box Other data validation involves entering whole numbers only 1 2 3 4 using the negative symbol or entering digits rather than alpha characters If you re typing over a default entry and get tripped up by the validation error message don t leave the box blank Default entries are usually identified in green italics near the data box allowing you to re enter those numbers as needed Be sure to Save your document often to avoid losing your work Moving Between Worksheet Tabs You will find multiple file tabs at the bottom of each worksheet These represent different windows within an Excel workbook For example there may be a summary report page or other worksheets Simply click on a file tab to go to that sheet In the rare event that you can t see all the file tabs available at the bottom of the Excel workbook screen you ll find a small horizontal bar on the same line This bar and its associated arrows that allow you to navigate left and right among the workbook tabs Excel help continued on next page Formulas and Calculations Formula cells are set up to calculate results based on data you provide in data entry cells Cells that calculate or reproduce data from other locations are shaded in blue green or yellow or other color Some versions of Excel al
36. o the Low Input Voltage then divides that by Module Hot Day Volts Vmin The result if not a whole number is raised to the next nearest integer The cushion is added to take into account the Start up Voltage which is higher than the Low Input Voltage Depending on the model a higher or lower cushion may be advisable so be sure to verify your choice with the manufacturer s sizing specs or configuration tool if there is one Maximum String Size Divides High Input Voltage over Module Cold Day Volts Vmax The result if not a whole number is reduced to the next lowest integer of Strings Maximum Divides the inverter s Max PV Current by the Module Short Circuit Current Isc The result if not a whole number is reduced to the next lowest integer of Strings Minimum Divides the Module Count by the Maximum String Size The result if not a whole number is raised to the next highest integer However if this number is higher than the Maximum of Strings the field will read out of range Inverter vs Array Watts First checks to see that the PV Array Watts yellow box don t exceed Maximum DC Watts If the Max DC Watts box is empty a second calculation is made comparing the inverter s AC watt rating to PV Array Watts Here a margin of acceptable difference is allowed PV Array Watts may be up to 15 higher than AC watts and up to 35 lower If these tests fail an error message appears
37. of columns exceeds 26 then two letters are used such as AA AB AC etc Worksheet2 B24 This indicates a cell located on another file tab inside the workbook In this example the tab is named Worksheet2 and the cell is B24 6699 two quotes symbols indicates empty cell lt gt neither greater than nor less than i e not equal to Printing Documents Depending on your edition of MS Excel your printing options may allow you to print out all the documents inside a workbook or only one at atime The Print function is located in the File drop down menu and may also be accessible by clicking on a printer icon Be sure to use the Page Break function to see if any page spills out across a print break If this happens adjust the worksheet margins How the Workbook Instructions are Presented Be sure to read the general instructions in the preceding section before starting work on your first worksheet Each set of workbook instructions is divided into the following categories e Purpose of this Workbook e Limitations Data Requested Calculations Extra Pages file tabs 1 ENERGY SAVINGS MEASURES Purpose of this Workbook The Energy Savings worksheet allows you to estimate savings from replacing incandescent light bulbs and old appliances The calculation of total kilowatt hours saved can then be used on the Utility Bill Audit which is key to sizing a grid tied photovoltaic array In addition th
38. on of space is needed to accommodate mid clamp attachment spacing of 1 inch and a 2 inch margin at the end of each row To change the spacing you must add or subtract from the module dimension Note Each module only needs to hold half the extra spacing Module Count Multiplies the Rows Possible by the Quantity per Row for Array 1 2 and 3 combined Modules Needed Divides Total DC Watts Needed by Module Watt Size If the result isn t a whole number it s converted to the next highest integer Is there enough space Compares the values in Module Count and Modules Needed If the number needed is higher than the count then the box will read No Otherwise the box will read Yes Extra Pages This workbook includes the following documents Resources Includes links to product pages and other array sizing tools Utility Rates Worksheet Allows you to tally the home s annual kWh usage as well as the percentage of which is charged at higher tier rates Instructions for completing the worksheet are provided earlier in this document See 3 Utility Bill Audit worksheet 5 TILTED ARRAY SIZING WORKSHEET Purpose of this Worksheet The Tilted Array Sizing worksheet determines how many modules will fit inside the array space s measured during the site survey along with the spacing needed between rows to avoid or minimize the shading that s caused by tilted modules Although most re
39. other reason If there isn t a spec for StartUp Voltage and you think it might be higher then the low range voltage then you can add a cushion in this data box Calculations Module Count Needed for Model Chosen Divides Array DC Watts Needed by STC DC Watts for the module brand selected and rounds up to the next integer Then compares the value with the one in Maximum Module Count fitting in the array space to make sure it s not larger than that amount If it is an error message is returned Try a larger module Otherwise the integer calculated appears in the box PV Array Size DC Watts Multiplies the module STC by the Module Count Module Temperature Range Check Check high low range against local record temperatures Module Hot Dav Voltage Vmin Multiplies the Power Max Temp Coefficient by the difference of temperature between 25 degrees Celsius and the Local High Temp then divides the result by 100 to get a 17 percentage then multiplies this result by the Power Max Voltage Vpm Module Cold Day Voltage Vmax Multiplies the Voltage Temp Coefficient by the subtraction of 25 degrees Celsius from the Local Low Temp then divides the result by 100 to get a percentage then multiplies this result by the Open Circuit Voltage Vpm Inverter Temperature Range Check Checks high low range against local record temperatures Minimum String Size Adds a cushion of 50 volts t
40. ral Repeats the value entered in Wire distance between Inverter and Main Panel Inverter Output Circuit EGC If a value is entered in Length for Ground Wire EGC for this circuit this cell repeats it However if no value is entered then this cell repeats the value of Inverter Output Circuit Neutral Steps 5 Perform Voltage Drop Calculations Array Strings This value was entered in Step 2 If a value wasn t entered a default of 2 will appear in this cell Source Circuit Voltage Drop Variables Operating Current This value was entered in Step 1 Wire Length The formula for this cell adds the Source Circuit Positive and Negative wire lengths from Step 4 to the sum of the module cables i e Module Count 2 Module Cable length 12 Note The division by 12 is needed to convert inches to feet Conductor Gauge This value was calculated in Step 1 Ohms per Kilofoot Looks up Conductor Gauge in NEC Chapter 9 Table 8 and returns the corresponding value Note The table s value for stranded wire rather than solid is used in all cases PV Output Circuit Voltage Drop Variables Operating Current If Combiner Box Reads Yes then the formula is Source Circuit Operating Current Array Strings If Combiner Box Reads No then the Source Circuit Operating Current is repeated here Wire Length The formula adds the PV Output Circuit Positive and Negative wire length values c
41. s by 2 If no value is entered a value of 4 is returned If Combiner Box is checked returns a value of 2 regardless of the value in Array Strings Conduit Adjustment If the amount in Conductors Exiting Box is under 4 the calculation returns a result of 100 per NEC Table 310 15 B 3 a If the amount is between 4 and 6 80 If between 7 and 23 9 70 If between 10 and 21 50 If higher the message out of range appears Temperature Adder If the box Check here if no conduit on roof is checked the message N A appears i e non applicable Otherwise this calculation takes the percentage in the Conduit Adjustment cell and returns the corresponding adder from NEC Table 310 15 B 2 C Temp Correction Factor If the Temperature Adder cell reads N A then this cell simply repeats the value in Temperature Correction Factor Step 1 Otherwise the calculation adds the Max High Temperature Step 1 to Temperature Adder then checks the sum in the ranges laid out in NEC Table 310 15 B 2 The cell returns the corresponding factor from the table Ampacity Calculation If the box Check here if no conduit on roof is checked the formula for this cell is Isc 1 56 Temperature Correction Factor Conduit Adjustment If the roof conduit box isn t checked the formula is Isc 1 56 Temperature Correction Factor Minimum Wire Gauge for Conductors Compares the amount in Ampacity
42. s the result by 100 Inverter Output Circuit Voltage Drop The formula for this cell is the Operating Current Length 1000 Ohms per Kilofoot The answer is expressed in volts Circuit Volts A fixed amount of 120 volts Percentage Divides Voltage Drop by Circuit Volts then multiplies the result by 100 All Circuits New Size If the box above this cell is checked the Conductor Gauge will be increased to the next beefier size If the box isn t checked the cell will remain empty Conductor Gauge If a gauge is entered in New Size than that value will be repeated here Otherwise the gauge calculated in earlier steps will appear New Voltage Drop Ifa value appears in New Size the voltage drop for that gauge will be calculated using the same formula from the earlier voltage calculations New Voltage Drop If a value appears in New Size the Percentage will be calculated using the same formula from the earlier Percentage calculations Steps 6 Compare wire gauge ampacities to any overcurrent device ratings All Circuits Overcurrent Ampacity Calculation This Conductor Gauge This cell repeats the value listed in Conductor Gauge at the very bottom of the previous page Derated Wire Ampacity Looks up the ampacity in NEC Chapter 9 Table 8 or 9 for the Conductor Gauge value to the left This value is then multiplied by the applicable derate factors from Steps 1 3 Temp Correction and Conduit Adjustment Not
43. sidential arrays are mounted flush atop a sloping roof occasionally a flat roof or area on the ground is used To receive direct sunlight the modules must generally be tilted at a angle that matches or is close to the site s local latitude The worksheet can also determine how many watts the array will produce It can compare this energy production against the kilowatt hour usage of the homeowner and calculate a percentage of grid offset Limitations Designed for a residence with a flat roof or available array space on the ground that faces southward Maximum annual kilowatt hour kWh usage must be under 14 000 Data Requested Annual Kilowatt Hour Usage This number is based on the Annual Kilowatt Hours determined on the Utility Bill Audit worksheet The highest value you can enter is 14000 The lowest is 1000 Daily Peak Sun Hours This number can be a general average retrieved by looking up the site s latitude on the NREL Data Sets or Redbook or available on many websites However a more reliable number can be provided by a Solar Pathfinder or Sun Eye shading analysis and report of the array location s Array tilt angles should also be factored into a Peak Sun Hour projection A default of 5 0 is provided Derate Factor This factor reduces the amount of array watt production based on wire losses projected system downtime module age soiling of the array and other common occurrences PV Watts provides a c
44. so show the formula in a box at the top left at the top of the document whenever the cell is selected Here s what some of the programming symbols represent all formulas begin with an equal sign addition subtraction multiplication division SUM A VG MAX CEILING ROUNDUP etc mathematical functions INT Transforms value into the nearest integer whole number SIN RADIANS trigonometric functions IF AND OR logical test functions Regarding the logical tests the most common one is whether or not all the data cells used in the calculation have been filled in If some data is missing the formula cell will either remain empty or display a zero An IF statement is divided in three parts each separated by a comma The first part is the logical test the second part is the result if the test returns a True result and the third part is the result if the test returns a False result Sometimes the third part is not filled with a result but another IF statement This allows the if this then that otherwise test to address multiple scenarios including NEC table ranges LOOKUP Data Table Location This function takes data entered in the worksheet and returns a corresponding value from a two row table located elsewhere in the worksheet E22 Any letter number combination indicates the location of a specific cell The letter signifies the column in the worksheet while the number signifies the row If the number
45. ters and bi modal inverters require a different set of calculations and are not considered here Data Requested Maximum Module Count fitting in array space Enter either the maximum number of modules that will fit in the array space This data was determined in the Array Sizing or Tilted Array worksheet Array Size in Watts This number may be taken from the Array Sizing or Tilted Array Sizing worksheets and is the value BEFORE the derating factor is multiplied to make it a smaller number The derate factor is not used in any calculations on the Modules and Inverter Sizing worksheet Alternatively you can try different array sizes in this field to check different array and inverter combinations Local Temperatures High Low Use the adjacent Solar ABC s link to find the record 15 temps for the site location In PV sizing the number most often used for the high temp is known as the 2 ASHRAE design temperature The temperatures will be used to calculate the highest and lowest possible voltages in the PV output circuit Be sure to use Celsius for all temps and include the negative symbol if it s listed Module Specs The following data fields pertain to a specific module that s being considered in a PV array To complete the fields you ll need to download the product literature and or spec sheet This material is typically available on the websites of online suppliers and module manufacturers
46. tt Size Enter the nameplate or STC wattage of the module brand and model you re considering For residential PV arrays the standard sizes are 185 235 240 and 250 13 Calculations Total Array DC Watts Needed Divides Annual Kilowatt Hours by Daily Peak Sun Hours X 365 then divides the result by the Derate Factor Inches Needed Between Rows This formula addresses multiple scenarios based on the site s latitude the range of which is first determined by a logical test The relevant formula e g 2 X module height is then applied Before this formula is applied the module must be calculated Height equals the SIN of the Array Tilt Angle which must be converted from degrees to Raidians for Excel multiplied by the sum of Module Length and Additional Row Width Rows Possible This calculation is divided into two parts First it checks to see if there s enough space for one row by adding Module base to the optional Added Inches then dividing the Area Width by that number If the answer is no then the box shows zero Otherwise the second part of the equation asks if there s space for more than one row Here Module Base is added to Inches Needed Between Rows and the optional Added Inches as a test If that result is larger then Area Width then Area Width is divided by the result and the new result is reduced down to the nearest integer and displayed in the box If the test fails then the box shows the n
47. umber One Quantity per Row Subtracts 3 5 inches from the Area Length then divides the result by the Module Width plus 0 5 inches The result is reduced down to the nearest integer The subtraction and addition of space is needed to accommodate mid clamp attachment and a 2 inch margin at the end of each row Module Count Multiplies the Rows Possible by the Quantity per Row for Array 1 2 and 3 combined Sizing a Tilted Array SL 2 Ba array tilt angle Row Spaces lt Base gt Module Base Uses the Pythagorean Theorem to calculate the amount of roof or ground space taken up by modules that are tilted upward thus reducing their footprint This value is needed in order to determine the number of row that will fit in an array space The formula for finding the Module Base dimension is SQRT Module Length 2 SIN RADIANS Tilt Angle Module Length 2 Modules Needed Multiplies Module Count by Module Watt Size Is there enough space Compares the values in Module Count and Modules Needed If the number of modules needed is higher than the count i e the quantity that will fit in the available array space s then the box will read No Otherwise the box will read Yes A Yes answer is required for an array configuration that will generate the needed power so you may need to change the Extra Pages This workbook includes the following documents that can be accessed b
48. what works best with the other variables on the worksheet It s recommended that an array be tilted at an angle equal to the site s latitude However where a manually adjusted tilt option is available the optimum tilt in winter is the latitude plus 15 degrees and latidue minus 15 degrees in summer In this scenario the maximum recommended tilt would be latitude plus 15 degrees The highest acceptable tilt angle for this worksheet is 89 degrees Additional Row Width Because different brands of racking and rails hold modules differently this field should only be completed with the equipment will add shading to the modules on either side of the row Be sure to factor in the inches on both sides A default of Zero is provided Module Length and Width These dimensions depend on the brand and model of the module you re considering To browse the spec sheets of different products use the links provide on the Resources page inside this workbook Note You might also consider using a landscape orientation instead of the usual portrait if this allows you to fit more modules into the array space To do this type your module s width into the worksheet s module length field and your module s length into the worksheet s module width field This will produce the correct calculations for a landscape scenario Default dimensions of 65 and 40 inches are provided for module length and width respectively Module Wa
49. y clicking on their file tabs at the bottom of the page Resources Includes links to product pages in order to research module and racking specs and other array sizing tools 6 Cost Payback Profit Analysis Note Please refer to the form help on the Resources tab of the workbook when completing this form No detailed instructions are included here Extra Pages This workbook includes the following documents that can be accessed by clicking on their file tabs at the bottom of the page Utility Bill Audit Worksheet Itemized Budget Resources and Help Detailed information is provided here along with online links 7 MODULES amp CENTRAL INVERTER INCLUDES STRING SIZING Purpose of this Worksheet After sizing an array space and determining the number of modules that will fit it s time to choose and configure the main components that will comprise the PV system This worksheet allows you to match an inverter and with a specific module model then determine the length and number of series strings Limitations Designed for a home photovoltaic system using one central 240 volt grid tied inverter with no battery backup You cannot use this form with microinverters or multiple inverters The size of the system must be under 10k 10 000 watts The maximum number of module series strings is four Battery banks hybrid systems 1 e incoporatingh a generator wind turbine or other energy sources standalone inver
50. y grid Limitations Designed for a U S residence Data Requested Wattage Measurements For each appliance or other electric load the following data should be entered Watts used by the Device ON OFF or Standby Hours the Device is ON OFF or Standby Plugged In per 24 hour day There are couple of ways to get the information One is to rent or purchase a household watt meter A popular brand is called Kill a Watt and may be available for check out from a public library The second method is to read the UL tag on the device or a spec sheet if you have a user s manual for it Sometimes the tag only lists the amps e g 1 5 A You can find out the watts by multiply this number by 120 volts that is if it s a common AC appliance running on a normal household circuit For computers and other digital electronics the amps listed may be DC In this case you ll need to find out how many volts the device uses then multiply amps times volts to get the watts Projected Conservation Measures For each device listed you ll have the opportunity to calculate energy savings by entering the following data Less Hours Device ON OFF or Standby per 24 hour day Cents per kWH rate This is the base rate charged by the utility company The data may be retrieved from the Energy Audit worksheet Calculations Annual Cost Multiplies Watts on and off by the number of hours then divides the total by 1000
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