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How to calculate the amount of kilowatt hours (kWh) your solar panel system will produce

Avatar for Ben Zientara
Published on 01/13/2012 in
Updated 12/14/2018
A calculator and a solar panel system

Interested to know how many kilowatt hours (kWh) your new solar panel system will kick out per year? It’s pretty simple to come up with a ballpark number. All you gotta do is look at the map below, which is labeled with an estimate of the number of kWh you can generate with one kilowatt (kW) of solar panels in every part of the United States.

If you haven’t gotten solar yet and you want to skip the ballpark estimates and have a professional use their high-tech software to give you an more exact estimate, connect with one of our trusted solar installer partners today.

If you’re ready for the ballpark, multiply the size of your system in kW by the number that is written in the shaded region where you live in the map below. Then multiply the result by 78%, to account for losses due to wiring and conversion from DC to AC power. Simple!

kwh_kwyear_map

Map Source

For example, let’s say you live in Nevada and are thinking about installing a 5-kW solar system. Most Nevadans live in the Las Vegas metro area, which is located in the shaded region labeled “2000.”

Take that 2000 and multiply by the 5 kilowatts of your system size to get 10,000 kWh. Multiply that by .78 to get 7,800 kWh, which is a good estimate of how much electricity your 5-kW system will produce in a year.

How much money can you save with solar panels?

Ah, here’s the tricky part. Electricity costs different amounts depending on your utility company. To make it more complicated, some utility companies charge a flat fee for electricity, while some charge different prices based on the time of day or season.

Let’s look at a simple example, using the data from above. People in Las Vegas get their electricity from NV Energy, which currently (no pun intended) offers a flat-rate of $.12/kWh for home customers.

Take the 7,800 solar kWh from the last step and multiply it by $.12/kWh, and you end up with $936 of savings per year. Pretty good!

You could further divide that $936 into 12 equal amounts to see that you’ll save an average of $78 per month. Note, that’s just an average, because solar panels don’t make the same amount of electricity all year round.

Unless you live at the equator, the angle of the sun in the sky changes based on the time of year. It’s low in the winter and high in the summer. Changes to weather patterns also affect how much sun your panels will get, though maybe not as much in the desert of southern Nevada as in the blue hills of northern Wisconsin.

How to estimate your own solar savings

Follow the steps above to see how much a 5-kW solar system could save you. Multiply the number in your area of the USA map by the size of your solar system in kW, then multiply the result by .78. Finally, multiply that by the price you pay per kWh from your utility company, and you’ve got an estimate of your annual savings!

To see how much you’d save with solar panels in Santa Ana, California, for example, you first have to discover that you pay $.25/kWh for electricity. Then, find that the Los Angeles area lies within the 1,900 number on the map, so the calculation for a 5-kW system would be: 5 kW x 1900 kWh/kW x 78% output x $.25, or $1,850 per year!

Or in Massachusetts, where electricity costs $.20/kWh, and a kW of solar panels makes about 1,500 kWh per year, the panels save you $1,170 per year. But Massachusetts has other great solar incentives, including the SMART Solar program, which will save you hundreds of dollars more every year.

Every state offers different electricity prices and incentives, and every roof is different, too. If you’re ready to bypass the guessing game using estimated numbers, get multiple solar quotes for your home from trusted professional installers, and check the math based on our site.

Last modified: December 14, 2018

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jerry johnsonErikTim PayneCharles Woodheadusv6428 Recent comment authors
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jerry johnson
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jerry johnson

seems to me that if you go with Wholesalesolar.com or gogreensolar.com both a DIY solar that will help you with all the necessary items, items needed, permit etc. A person should in the beginning do all they can to reduce the amount of electricity they use. LED lights, turn down the thermostat during the evening. Using window coverings that will keep either the heat or the cold out. Solar should be the last alternative. Then you have to realize that its not free. Your paying a monthly payment for electricity, the same as with solar panels, the big difference is… Read more »

Erik
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Erik

Charles is right and after putting it off for years finally a guy comes a long and gets me locked in 25 year to own the panels. Only makes a 20$ save in my pocket. I saved more money not having solar and even with my normal electric bill. My power bill is still about $190.00 a month which some months its only $184.00 + tax. But add on my solar bill which is $185.00. Yes im paying over $300.00 a month. Doesn’t help sell a house when its not going to save a dime. Waste of money!

Charles Woodhead
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Charles Woodhead

The savings estimated are nonsense because until the system has paid for itself, you’re saving nothing. If you paid $20,000 for you wonderful system and it produces $936 per year it’s going to take 21+ years to break even. $1850 per year – 10.81 years. Until then you save nothing. Who’s going to fix your system when it breaks? How fast are they going to respond? If you’re Northern tier and it’s January, do you think they’re going to rush up on your snow covered roof to fix it. If you’re on the grid and the system goes down, you… Read more »

Tim Payne
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Tim Payne

We are having solar panels installed next month. In our case, we are paying $25,000 for our system. The 30% tax credit means we actually pay $17,500. We are financing it at 2.99%. Instead of using the tax rebate to pay down the loan @ 2.99%, we are paying off a credit card @ 18%. Over 5 years we will save about $6,000 in interest on that card. So, now our cost is $10,750. In addition, studies have shown the increase in property value is about 3.5%. That is a $12,250 increase immediately on our $350,000. That means if we… Read more »

usv6428
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usv6428

How much should a Panasonic VBHN335SA17 solar panel produces per day? I’m getting between 1.20 kWh to 2.06 kWh per panel on a 27 system on the same roof. I want to know why the variation. I’m in San Jose, CA.

Dianna
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Dianna

I’m trying to determine my SRECs. According to my energy company’s bill, I used 900 kwh and had an excess generation of 1226 kwh. How much would the SREC be? Would I add both to determine or would I just use the excess kwh used?

Terry
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Terry

My power company (APS in AZ) only credits me with about 70% of what my solar monitoring site reports that I generate. A friend is only getting credit for 47% of what he generates according to his solar monitoring system. Why is there such a discrepancy?

Bubba solar
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Bubba solar

Your house is using power while the panels are generating. Let’s say you use 10kwh during the daylight hours. Your system generates 25kwh in the same time you then have a credit for the night of 15kwh, you generated 25 but only 15 would be shown as a credit.

Toussaint
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Toussaint

Thank you for your explanations concerning radiance charts and the 0.78 conversion factor. I have a 17 panel system, each panel at 305W, in Las Vegas, and the calculation is right on the money. 2000 x 5.185 kW = 10,370 kWh x 0.78 = 8089 kWh/year x $0.12/kW = $970 savings/year. The Fed Tax rebate was 30% on the total install cost, and NV Energy rebated $1100. My payback in full will take 10 years. The panels are rated for 25 years minimum.

Anonymous
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Anonymous

“Unless you live at the equator, the angle of the sun in the sky changes based on the time of year.” *blink, blink* The earth is still tilted, even if you live at the equator.

SREE
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SREE

100 WATS – 02Nos SOLAR PANEL WITH ME.I WANT TO USE THIS FOR 90 WATTS LED STREET LIGHTING.WHAT IS THE CAPACITY REQUIRED FOR THE STORAGE 12 VOLT BATTERY (Ah)

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