Calculate How Much Solar

First, you need to understand the electricity consumption of the property. You can find it with your 12 month utility bill. Add monthly kilowatt-hours (kWh) to the annual total. If you don’t have an electric bill, there are other ways to get an estimate. Order solar design services and we can help. Once you know the kilowatt-hours you need, use the calculator here to determine how many kilowatts (kW) of solar energy you need to produce a kilowatt-hour.

Growatt inverters

solar calculator

  1. Enter the kWh used per year:
  2. Find the solar hours for each day (see table below)
  3. Enter the percentage of electricity bill you want to pay
  4. Click Calculate
  5. This is the solar array size in kW

Next, now that you’ve estimated the kilowatts you’ll need, look at solar kit sizes to compare prices, brands, and options.

Remember, you decide how much solar power you get based on your needs, available space, and budget. There is no requirement that you have to offset 100% of your current energy use. Utilities typically allow grid-tied systems to use 120% of the previous 12-month consumption. They will also take into account increased consumption from electric vehicles, home extensions or other needs.

Solar Kit Sizes

Find solar kits based on the amount of kilowatts (kW) you need to live with. Use this list to select a kW size, from 1kW or 1,000 watts to 1mW or 1 million watts.

Buy the right size solar system at low wholesale prices. These pre-engineered solar panel systems are specifically designed to provide renewable energy to your home or business, and they include every component you need to build your own power system.

Popular Solar Kit Sizes


solar hours per day

The table below provides daily solar hour lookups for the largest cities in each US state. Use the daily solar hours in the calculator above. If you know the kilowatt-hours your property consumes annually, divide that by the kilowatt-hours per 1kW to determine the solar array size you need for your project.

AlabamaBirmingham5.261,422 MarylandBaltimore4.831,437
AlabamaHuntsville5.08 1,418 MassachusettsBoston4.721,339
AlabamaMobile5.491,540 MassachusettsSpringfield4.881,391
AlabamaMontgomery5.431,513 MichiganDetroit4.601,325
AlaskaAnchorage3.401,053 MichiganGrand Rapids4.481,280
ArizonaFlagstaff6.211,695 MinnesotaDuluth4.371,278
ArizonaPhoenix6.521,753 MinnesotaMpls/St Paul4.621,320
ArizonaTucson6.541,807 MississippiJackson4.471,277
ArkansasLittle Rock5.181,401 MissouriKansas City5.041,414
ArizonaFlagstaff6.211,695 MissouriSpringfield5.161,412
ArizonaPhoenix6.521,753 MissouriSt. Louis4.991,387
ArizonaTucson6.541,807 NebraskaLincoln5.021,436
ArkansasLittle Rock3.401,401 NebraskaOmaha5.021,425 
CaliforniaBakersfield6.161,714 NevadaLas Vegas 6.371,764
CaliforniaFresno5.961,636 NevadaReno 5.991,697 
     New HampshireConcord4.831,303
CaliforniaLos Angeles6.131,708 New JerseyNewark4.741,313
CaliforniaModesto5.96 1,652  New MexicoAlbuquerque6.411,805
CaliforniaOakland5.62 1,598 New YorkBuffalo4.341,221
CaliforniaOxnard6.04 1,702  New YorkNew York City4.581,310
CaliforniaRiverside6.28 1,790 New YorkSyracuse4.211,159
CaliforniaSacramento5.83 1,620  North CarolinaCharlotte5.181,419
CaliforniaSalinas5.61 1,598 North CarolinaWilmington5.291,493
CaliforniaSan Bernardino6.20 1,714  North DakotaBismark4.721,364
CaliforniaSan Diego5.701,627  OhioCincinnati4.681,301
CaliforniaSan Francisco5.561,593  OhioCleveland4.681,290
CaliforniaSan Jose5.861,667  OhioColumbus4.571,296
ColoradoColorado Springs5.721,614 OhioDayton4.701,330
ColoradoDenver5.691,59 OhioToledo4.621,326
ColoradoFort Collins5.19 1,455  OklahomaOklahoma City5.541,579
ConnecticutBridgeport4.631,307 OregonPortland4.091,118
ConnecticutHartford4.68 1,273  PennsylvaniaPhiladelphia4.781,334
DCWashington4.871,391 PennsylvaniaPittsburgh4.461,210
FloridaFort Lauderdale 5.741,662 Rhode IslandProvidence4.741,334
FloridaJacksonville5.52 1,478  South CarolinaCharleston5.381,489
FloridaMiami5.77 1,623  South DakotaSioux Falls4.881,441
FloridaOrlando5.64 1,570  TennesseeClarksville4.481,394
FloridaTallahassee5.41 1,446  TennesseeKnoxville5.001,397
FloridaTampa5.761,610  TennesseeMemphis5.181,470
GeorgiaAtlanta5.261,470  TennesseeMurfreesboro4.971,404
GeorgiaSavannah5.34 1,459  TennesseeNashville4.911,390
HawaiiHonolulu5.871,683 TexasAmarillo6.081.735
IdahoBoise5.171,439 TexasDallas5.501.552
IllinoisChicago4.551,307 TexasHouston5.331.476
Illinois Springfield4.621,331 TexasSan Antonio5.541.545
IndianaFort Wayne4.611,317 UtahSalt Lake City5.321,554
IndianaIndianapolis4.721,342 VirginiaRichmond5.061,360
IowaDes Moines4.791,362 WashingtonSeattle3.971,157
KansasKansas City5.041,464 WashingtonSpokane4.381,228
KansasWichita5.381,553 WisconsinMilwaukee4.621,339
KentuckyLouisville4.811,389 WyomingCheyenne 5.461,574
LouisianaNew Orleans5.411,524 WyomingCody5.001,478

The Solar Hours per Day table uses these input criteria for the PV Watts calculation for each location:

  1. Module Type – Advanced 19% or better efficiency
  2. Array Type – Fixed (Roof Mount)
  3. System Loss – 12% Standard or 15% Snow County
  4. Tilt – 20 degrees
  5. Azimuth – 180 degrees
  6. Inverter Efficiency – 98

Actual results for each project will vary.

Solar Power Map of the United States

Find your Solar Hours per Day using the color-coding on this map. Enter the value for your location into the solar calculator.

A sun map uses insolation, a measure of the amount of solar radiant energy received at a given surface area over a given period of time. This is usually measured in kilowatt hours per square meter per day (kWh/m2/day). This map shows the average daily total solar radiation for the entire United States. It was developed by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).

Steps to Calculating How Much Solar Energy You Need

Growatt inverters

At Growatt inverters, we make solar easy, calculating how much solar you need has never been easier. On our Calculate How Much Solar Energy page, you’ll find out how many kilowatts or kilowatts of solar energy are needed to produce the kilowatt-hours or kilowatt-hours of energy your property uses.

To estimate the size of your solar system, you need three pieces of information to calculate solar kilowatts.

Your utility bill for the past 12 months
1.The solar hours per day at your location
2.The percentage of your electricity bill you want to pay
3.Now, let’s look at each of these in more detail.

your electricity bill
It would be best if you have monthly electricity bills for a year. On each electric bill, find the kWh or kWh for each month. That’s how much energy you expend. Some utility bills have summary sheets. You’ll probably find your kWh there. A summary graph may show average daily kWh usage over the last 12 months. If so, you can enter the total kWh for the year.

If a total is not provided, add the kWh for each month and enter the total into #1 of our solar calculator. Do not include commas or decimal points. For example, the average household in the United States uses 30 kWh of electricity per day. Multiply that by 365 days, and the average American household uses 11,000 kWh of electricity per year. So let’s enter 11000 in field #1.

solar hours per day
The next piece of information to look at is the daily solar hours for your location. In the United States, the average solar hours per day is between 4-6 hours. Average solar hours per day. Summer is long and winter is short. Now, scroll down the page to find the solar hours for your state and nearest city. For our example, let’s use the first position in the list. Every day in Birmingham Alabama has 5.26 solar hours. Enter this number into #2, Solar Hours per day.

Electricity Offset
The last piece of information is the amount you will pay for your electricity bill. 50%, 80%, 100%, 150%; it’s up to you. But let’s start with 100. Enter the integer into #3 without the % sign. For our example, you should enter #1 11000, #2 5.26, and #3 100 You can hit calculate!

The example answer should be 7.64. This means that in Birmingham, Alabama, 7.64 kilowatts or 7,640 watts of solar should generate 11,000 kWh per year. You now know how to calculate the kilowatt size required for a solar kit that will produce the kilowatt hours you consume. To find solar kit prices and more details, click on the red link to View Solar Kit Sizes, or use the menu by selecting Solar Kit, then Solar Kit Size.

You’ll see we have solar kits in many different sizes, from 1,000 to 1,000,000 watts. Sun Watts. Solar energy made simple.

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