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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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Lunarstudio RenderingsSean Rooney, Realtor - Brokered by EXP Realty LLCjerry johnsonErikTim Payne 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
Guest
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
Guest
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
Guest
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 »

Sean Rooney, Realtor - Brokered by EXP Realty LLC
Guest
Sean Rooney, Realtor - Brokered by EXP Realty LLC

Tim, you came to the same conclusion we did. Buy the system #1. Then find a reasonable interest rate. We used a HELOC product taking advantage of home equity, and will also be able to deduct the interest. When we get the 30% tax credit back, it will go directly to paying the principle of the loan. System was 24k, and that included a hybrid water heater that saved us 6 panels for a total of 21 (Solaria 355w). It should increase property value as long as you use a solar certified appraiser who understands the value, AND in FL… Read more »

Lunarstudio Renderings
Guest

This also depends on where you live in the state and what local and state incentives you may have. Our system is 5.92 kWH at close to 20k total. We’re on a MLP (municipal electric) and our rates are tiered somewhere between .12-.19 cents the last I checked. Currently, the DOER has incentives Since April 2019 (assuming your roof and location qualifies) for $1,200 per kWH DC up to 50% or $30,000. So that means we will receive a rebate of around $6,000 bringing our system down to $14k. The town has a maximum rebate of $3,125 bringing it down… Read more »

usv6428
Guest
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
Guest
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
Guest
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
Guest
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
Guest
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
Guest
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
Guest
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)

John
Guest
John

Beginning stages (with a solar expert) of planning a 20-Megawatt solar array on family farm in SE Nebraska. I have calculations based on 1700 irradex, for 5 hrs at using a .15 efficiency index for the panels. What will be the estimated total potential annual output considering the reductin tion (78%)? Looking for a preliminary corroboration of my calcs only..

anonymous
Guest
anonymous

I see a lot of questions from people asking for help to calculate what they need for their specific situation. You can estimate this yourself using the info on this page. I recently had a solar system installed so I will share the related calculations for my actual system which may help others do the same for their specific scenario. I live in NJ and my town has its own electric company. The rates are fairly expensive so that made our decision to install a solar system a little easier. However, I’m skeptical by nature and didn’t fully believe the… Read more »

Earl
Guest
Earl

Don’t get sucked into this price per/watt install prices these companies would have you believe.. nonsense! It’s now 2018, solar gear and tech is cheap. Branded LiFePO4 batteries last for 20 years as with these new 300w panels. If you can install yourself do it! save thousands.. but just don’t get ripped off by these horrible companies.

Rusty J
Guest
Rusty J

What a great idea, spending $28,000 to save $78 per month, let’s see, that would take only 29 years to pay it off. And then I wonder what Solar technolongy will be available then….

tolenna joe
Guest
tolenna joe

base on the radiance chart, what would be the number for kosrae, micronesia please help

Lynn Harding (@Lynn9711SATX)
Guest
Lynn Harding (@Lynn9711SATX)

Thank you for this informative article! It helped provide a frame of reference for determining what to expect each month when our 6.36kW grid-tied solar panel system is fully functioning!

joey
Guest
joey

hello, i just want to know what is kwh and kw?? very difficult to understand about these things. energy and power?? is anyone want to explain??

sheldon
Guest
sheldon

cool

Kerryslanemd@att.net
Guest

I want to buider a solar farm in NJ approx 240,000 Sq ft. How much electricit will it produce? Annual income at 20 cents kwH?

matt
Guest
matt

Great infomration here. 1 question, why am I multiplying by 78%? I dont understand where that 78% is coming from.

Shiv Baghel
Guest
Shiv Baghel

i want to produce 1kilowatt eelectricity per hour….how many solar plate used in production and details of solar panels like daimeter length etc..

Lloyd
Guest
Lloyd

How many Solar kilowatts (or kwh) does Indiana produce annually?

saurav upadhyay
Guest
saurav upadhyay

if my electricity bill cost for 163 kwh units in one month ,what cost charged is be for solar panel system for my 163 units cosumption in solar panel ,please calculate and tell me which is cheap

mayur
Guest
mayur

i want to get information about will home solar system work in mansoon season? give me quatation of 50 kw to 100 kw panel on my mail id

Essam moqbel
Guest
Essam moqbel

I consume an average of 4.5kw/day to run a 200w fridge and a100w TV for 10hours plus total of 500w/d lighting.What size of solar panels(KW/h) do i require to give me this daily capacity; please note that i live in the middlest,Yemen therefore need the solar system not for annual savings for my electricity bill rather than providing alternitive source of power which is currently upsent in our region ,also what type&size of batterries are required to store the power needed during the night which is about 60% of the daily4.5kw.your kind help would be very apprecieted.

Junior Madjani
Guest
Junior Madjani

I am an engineer currently working for a Gold mine. i am currently looking at a cost saving project of installing solar panel systems for our Mills. Our mills generate approximately 4500 Kwh, how many solar panel do need to install in order to generate that? please help.

tophermiller
Guest
tophermiller

Very helpful. But one question: Does this calculation assume AC kw or DC kw for the system size parameter?

Anonymous
Guest
Anonymous

If I am charged .09 per kwh and the monthly bill is roughly $15,000, how many kwh would I need to produce in order to reduce my bill to zero?

Anonymous
Guest
Anonymous

GaelanClark writes….Solar City is selling their services in Colorado. Their contract shows a price per kwh of $0.109. The price per kwh of electricity from non-renewable energy in Colorado is $0.112. A difference of $0.003 per kwh!!! So under the above assupmtions we can calculate the actual “savings” a solar customer would realize. Colrado is in the “1900” region…1900*78%=1482…1482/12(*5)=617.5 kwh per month. 617.5*.003=$1.85 dollars per month!!!! WOW!!! AMAZING SAVINGS!!!! And, you would still need to be plugged into the grid and you would still be receiving a bill from your local power provider, so in fact, your bill would be… Read more »

Anonymous
Guest
Anonymous

You can use the light generated by light bulbs or led lights to generate energy with solar panels, but the power you get out of the panels will be way less than the power you use to run the light bulb

Anonymous
Guest
Anonymous

I have a monthly bill of 900kw used. How much panels sys , will I needed for that . I am living in Turks and Caicos Islands.

Anonymous
Guest
Anonymous

Which is better 3.57 kw for $17,493 or 3.71 kw for $18,179? How many panels is for 3.57 and 3.71?

Anonymous
Guest
Anonymous

Hello..can we generate power through light bulbs or high light emitting bulbs like traffic lights using solar pannels

Anonymous
Guest
Anonymous

its very useful to me thanks a lot

Anonymous
Guest
Anonymous

this is great info. dont forget that our energy companies usually charge for alot more than just the generation amount. there’s usually transmission, distribution, and other customer and gov fees. if you’re looking to see how much you’ll offset, make sure to include these especially if they’re charged on a per kwh basis. for instance in PA, my generation charges are only 8.2c /kwh but after all the other fees I end up paying about 12c/kwh.

Anonymous
Guest
Anonymous

I live in the 200 region and the numbers appear close based on what I see. I might add if you live in CA its about $.20 /KWH average not anywhere near $.11.

Anonymous
Guest
Anonymous

Help me figure this out. Using SRP’s time of use plans gets my electric cost down to $0.07 kWh from 10 am to 1pm which allows me to keep my AC off for the rest of the daylight hours. Doesn’t that drop the annual figure of 7800 kWh in half? Even if it’s 4000 kWh, my annual savings would only amount to $280, right? ($0.07 X 4000)

Anonymous
Guest
Anonymous

DOE stands for “Depratment of Energy” (US). While I didn’t find the exact map on the DOE website, here is another US government website with the solar radiance data. YOu will see that the maps look pretty similar: http://www.nrel.gov/gis/solar.html

Anonymous
Guest
Anonymous

DOE stands for “Depratment of Energy” (US). While I didn’t find the exact map on the DOE website, here is another US government website with the solar radiance data. YOu will see that the maps look pretty similar.

Wynn
Guest
Wynn

Dan: Very helpful stuff here. Thank you. Can you explain what those numbers (2000 for AZ) from the radiance chart actually mean?

deependra
Guest
deependra

i have read many articles about set up of solar system, initial coast have heavy amount. i have land for agriculture and i want electricity through solar for every operation.but i cant understand about role of my indian govt.

fakhrul
Guest
fakhrul

how did you come up with 78% and where did you get the map? how was the map developed?

Dave Llorens
Member

Hi Fakhrul,

The map is a solar radiance chart from DOE. 78% reflects the total assumed energy delivered by your solar system accounting for three specific losses:

PV Energy delivered as % of manufacturers rating: 95%
Wiring & power point tracking losses: 9% (91% delivered)
Inverter Efficiency: 90%
Total Energy Delivered 95% x 91% x 90% = 78%

eunoia16
Guest
eunoia16

Can you cite your source please? What’s DOE?

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