How many solar panels do I need?

Divide your annual kWh by your state's yield per kW, then by the panel's rating. In Arizona, 10,800 kWh needs about 5.5 kW, fourteen 400 W panels. In Washington the same use needs about 8 kW.

How much electricity does a kW of solar produce?

Nationally, EIA's 2024 estimates for small-scale solar work out to about 1,660 kWh per kW per year. The highest states, New Mexico, Nevada and Arizona, are near 2,000; Pennsylvania and Alaska are between 1,040 and 1,090.

How much does a solar system cost?

HomeAdvisor's June 2026 guide gives $2.50 to $3.50 per watt installed, about $15,000 to $21,000 for 6 kW before incentives. Lawrence Berkeley National Laboratory's Tracking the Sun puts most residential systems installed in 2023 at $3.20 to $5.50 per watt.

Why is Rhode Island not used?

EIA's small-scale solar capacity for Rhode Island falls from 453.2 MW to 224.4 MW between the end of 2023 and the end of 2024 in the same table, which makes the per-kW figure 832, far below neighbouring states. The calculator uses the national figure instead.

Is EIA's solar generation measured?

No. EIA says utilities do not necessarily know how much rooftop PV generates, so it estimates small-scale generation from the data it collects from utilities and third-party owners.

What size wire for solar panels?

Wire size depends on the circuit's current, termination rating and conditions, not on the panels as such. The wire size calculator applies the residential code's ampacity rules.

How long do solar panels take to pay back?

Divide the installed cost by the annual value. At $2.50 to $3.50 per watt, a 5.5 kW Arizona system saving about $1,670 a year takes roughly 8 to 12 years before any change in electricity prices or export credit.

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Solar Panel Calculator

EIA estimated small-scale solar generation and capacity, by state

A kilowatt of rooftop solar produced about 2,030 kWh in New Mexico in 2024 and about 1,090 in Pennsylvania, by the federal government's own estimates of every small system in each state. That is the number that sizes an array, and this calculator uses it. It also notes what a leading price guide still gets wrong in 2026: it prints costs after a 30 per cent federal tax credit that the IRS says ended with 2025.

System size from your electricity use

State

Annual electricity use

kWh

Share to cover

Panel rating (0 to skip)

Annual use is on your utility bill or account, often as a 12 month history. Share is how much of it you want the panels to cover.

Specification summary

Generated from on . Reopen that address to reproduce these figures exactly.

Entered

Result

What a kilowatt of rooftop solar produced

Solar installation prices

Installed
Item	Low	High	Unit
Installed price	$2.50	$3.50	per watt
5 kW system	$12,500	$17,500	system
6 kW system	$15,000	$21,000	system
8 kW system	$17,600	$28,000	system
10 kW system	$25,000	$35,000	system
12 kW system	$30,000	$42,000	system

Source: HomeAdvisor, how much does solar panel installation cost. Last price check: September 13, 2026.

The source says it was updated using automation technology and reviewed by an editor. It also prints a column of costs with a 30 per cent federal tax credit and says the credit runs to 2032; the IRS says the Residential Clean Energy Credit is not available for property placed in service after December 31, 2025, so that column is left out. Its own table breaks its per-watt pattern on the 8 kW row, and prints the 7 kW row with the credit identical to the row without it. Lawrence Berkeley National Laboratory's Tracking the Sun puts the middle 60 per cent of residential systems installed in 2023 at $3.20 to $5.50 per watt.

Worked example

A house in Arizona using 10,800 kWh a year, covered in full with 400 W panels, then the same use in Washington.

Yield. EIA's 2024 estimates give Arizona's small-scale solar 1,953 kWh per kW.
Size. 10,800 ÷ 1,953 = 5.53 kW.
Panels. 5,530 W ÷ 400 W = 13.8, so 14 panels, 5.60 kW.
Value. 10,800 kWh at Arizona's 15.45¢ residential average is about $1,669 a year.
Washington. At 1,357 kWh per kW, the same use needs 7.96 kW, 44 per cent more panels.

The same house needs nearly half as much again in panels in Washington as in Arizona, and saves less per kWh there because power is cheaper. Size is a state question before it is a roof question.

The formula

Two divisions:

system kW = annual kWh to cover ÷ kWh per kW in your state panels = system W ÷ panel W, rounded up

kWh per kW: EIA 2024 estimated small-scale generation divided by the average of year-end 2023 and 2024 small-scale capacity
annual kWh: twelve months of use from the utility
panel W: the panel's rated power on its data sheet
price: published installed price per watt, before incentives

The yield is the average of systems already on roofs, so a well oriented new array usually does better and the size here errs large.

Why this page does not use a sun hours map

Solar calculators multiply by peak sun hours and a loss factor, and rarely say where either came from.

The Energy Information Administration estimates how much every small solar system in each state generated and how much is installed. Dividing the two gives a figure that already contains real roofs, real shade and real losses.

Checking the table exposed one state whose capacity halves in a year, and checking the price guide exposed a federal credit it still applies after it ended. Both are on the page.

Estimated small-scale solar yield by state
State	Small-scale generation, 2024	Capacity, end 2023 to end 2024	kWh per kW, 2024	Residential price, 2026 to June
Alabama	27 GWh	15.8 to 17.0 MW	1,646	16.58¢
Alaska	20 GWh	19.2 to 19.2 MW	1,042	26.86¢
Arizona	5,446 GWh	2,679.6 to 2,896.3 MW	1,953	15.45¢
Arkansas	511 GWh	250.5 to 333.9 MW	1,749	13.43¢
California	31,724 GWh	16,615.2 to 18,209.2 MW	1,822	33.17¢
Colorado	2,035 GWh	1,089.0 to 1,201.2 MW	1,777	16.65¢
Connecticut	1,458 GWh	978.6 to 1,132.3 MW	1,381	28.82¢
Delaware	203 GWh	130.1 to 143.5 MW	1,484	17.74¢
District of Columbia	257 GWh	142.2 to 176.1 MW	1,615	24.54¢
Florida	4,611 GWh	2,582.3 to 2,819.9 MW	1,707	15.36¢
Georgia	568 GWh	320.2 to 342.4 MW	1,714	15.19¢
Hawaii	1,573 GWh	833.8 to 918.1 MW	1,796	45.95¢
Idaho	276 GWh	156.0 to 177.6 MW	1,655	12.80¢
Illinois	1,730 GWh	1,164.1 to 1,372.4 MW	1,364	19.22¢
Indiana	387 GWh	238.1 to 270.3 MW	1,522	17.11¢
Iowa	478 GWh	286.4 to 332.8 MW	1,544	13.77¢
Kansas	166 GWh	87.8 to 108.6 MW	1,690	15.19¢
Kentucky	161 GWh	93.5 to 110.4 MW	1,579	14.37¢
Louisiana	336 GWh	185.1 to 202.6 MW	1,733	13.51¢
Maine	1,015 GWh	532.9 to 849.4 MW	1,469	29.67¢
Maryland	1,479 GWh	1,038.0 to 1,132.4 MW	1,363	21.27¢
Massachusetts	4,058 GWh	2,661.3 to 2,966.5 MW	1,442	30.06¢
Michigan	346 GWh	226.4 to 270.0 MW	1,394	21.14¢
Minnesota	403 GWh	243.2 to 296.1 MW	1,495	15.98¢
Mississippi	30 GWh	14.4 to 18.4 MW	1,829	15.35¢
Missouri	742 GWh	403.2 to 439.8 MW	1,760	13.45¢
Montana	107 GWh	59.0 to 81.8 MW	1,520	13.77¢
Nebraska	57 GWh	33.0 to 36.0 MW	1,652	12.70¢
Nevada	2,042 GWh	952.5 to 1,124.3 MW	1,966	13.79¢
New Hampshire	361 GWh	232.8 to 270.4 MW	1,435	26.83¢
New Jersey	3,395 GWh	2,297.4 to 2,489.6 MW	1,418	23.65¢
New Mexico	800 GWh	375.3 to 411.6 MW	2,033	14.82¢
New York	4,522 GWh	2,995.2 to 3,394.0 MW	1,416	29.26¢
North Carolina	908 GWh	498.1 to 579.2 MW	1,686	14.90¢
North Dakota	3 GWh	2.2 to 2.2 MW	1,364	12.19¢
Ohio	508 GWh	341.2 to 411.9 MW	1,349	18.53¢
Oklahoma	229 GWh	110.9 to 145.1 MW	1,789	13.37¢
Oregon	618 GWh	398.1 to 476.8 MW	1,413	15.31¢
Pennsylvania	974 GWh	811.8 to 984.0 MW	1,085	20.90¢
Rhode Island	282 GWh	453.2 to 224.4 MW	not usable	29.45¢
South Carolina	637 GWh	378.1 to 400.2 MW	1,637	16.04¢
South Dakota	7 GWh	3.8 to 5.4 MW	1,522	14.33¢
Tennessee	86 GWh	53.5 to 58.6 MW	1,534	13.90¢
Texas	4,956 GWh	2,803.0 to 3,072.0 MW	1,687	16.11¢
Utah	995 GWh	522.1 to 586.3 MW	1,795	13.17¢
Vermont	245 GWh	174.4 to 185.7 MW	1,361	23.98¢
Virginia	1,044 GWh	592.8 to 690.1 MW	1,628	16.69¢
Washington	634 GWh	430.7 to 503.6 MW	1,357	14.35¢
West Virginia	61 GWh	35.7 to 44.8 MW	1,516	15.42¢
Wisconsin	369 GWh	215.2 to 271.7 MW	1,516	18.99¢
Wyoming	33 GWh	17.4 to 21.7 MW	1,688	13.88¢
U.S. Total	83,918 GWh	47,774.7 to 53,228.1 MW	1,662	18.16¢

Read 2026-09-13. EIA Electric Power Annual 2024 Tables 3.21 and 4.7.B; Electric Power Monthly Table 5.6.B.

Download this table as CSV. Same cells as printed above, nothing added.

What a kilowatt of rooftop solar produced in each state

The Energy Information Administration estimates how much electricity small-scale solar generates in every state, and how much of it is installed. It is candid that the first figure is an estimate:

Because electric utilities do not necessarily know how much electricity is generated by rooftop PV on their distribution systems, generation from these systems must be estimated.

Divide 2024 generation by the average of the capacity at the end of 2023 and 2024 and you have what a kilowatt of real rooftop systems produced that year, across all their tilts, directions and shade. Nationally it is 1,662 kWh. The highest are New Mexico 2,033, Nevada 1,966, Arizona 1,953; the lowest Alaska 1,042, Pennsylvania 1,085, Ohio 1,349.

EIA estimated small-scale solar by state. kWh per kW is this page's arithmetic
State	Small-scale generation, 2024	Capacity, end 2023 to end 2024	kWh per kW, 2024	Residential price, 2026 to June
Alabama	27 GWh	15.8 to 17.0 MW	1,646	16.58¢
Alaska	20 GWh	19.2 to 19.2 MW	1,042	26.86¢
Arizona	5,446 GWh	2,679.6 to 2,896.3 MW	1,953	15.45¢
Arkansas	511 GWh	250.5 to 333.9 MW	1,749	13.43¢
California	31,724 GWh	16,615.2 to 18,209.2 MW	1,822	33.17¢
Colorado	2,035 GWh	1,089.0 to 1,201.2 MW	1,777	16.65¢
Connecticut	1,458 GWh	978.6 to 1,132.3 MW	1,381	28.82¢
Delaware	203 GWh	130.1 to 143.5 MW	1,484	17.74¢
District of Columbia	257 GWh	142.2 to 176.1 MW	1,615	24.54¢
Florida	4,611 GWh	2,582.3 to 2,819.9 MW	1,707	15.36¢
Georgia	568 GWh	320.2 to 342.4 MW	1,714	15.19¢
Hawaii	1,573 GWh	833.8 to 918.1 MW	1,796	45.95¢
Idaho	276 GWh	156.0 to 177.6 MW	1,655	12.80¢
Illinois	1,730 GWh	1,164.1 to 1,372.4 MW	1,364	19.22¢
Indiana	387 GWh	238.1 to 270.3 MW	1,522	17.11¢
Iowa	478 GWh	286.4 to 332.8 MW	1,544	13.77¢
Kansas	166 GWh	87.8 to 108.6 MW	1,690	15.19¢
Kentucky	161 GWh	93.5 to 110.4 MW	1,579	14.37¢
Louisiana	336 GWh	185.1 to 202.6 MW	1,733	13.51¢
Maine	1,015 GWh	532.9 to 849.4 MW	1,469	29.67¢
Maryland	1,479 GWh	1,038.0 to 1,132.4 MW	1,363	21.27¢
Massachusetts	4,058 GWh	2,661.3 to 2,966.5 MW	1,442	30.06¢
Michigan	346 GWh	226.4 to 270.0 MW	1,394	21.14¢
Minnesota	403 GWh	243.2 to 296.1 MW	1,495	15.98¢
Mississippi	30 GWh	14.4 to 18.4 MW	1,829	15.35¢
Missouri	742 GWh	403.2 to 439.8 MW	1,760	13.45¢
Montana	107 GWh	59.0 to 81.8 MW	1,520	13.77¢
Nebraska	57 GWh	33.0 to 36.0 MW	1,652	12.70¢
Nevada	2,042 GWh	952.5 to 1,124.3 MW	1,966	13.79¢
New Hampshire	361 GWh	232.8 to 270.4 MW	1,435	26.83¢
New Jersey	3,395 GWh	2,297.4 to 2,489.6 MW	1,418	23.65¢
New Mexico	800 GWh	375.3 to 411.6 MW	2,033	14.82¢
New York	4,522 GWh	2,995.2 to 3,394.0 MW	1,416	29.26¢
North Carolina	908 GWh	498.1 to 579.2 MW	1,686	14.90¢
North Dakota	3 GWh	2.2 to 2.2 MW	1,364	12.19¢
Ohio	508 GWh	341.2 to 411.9 MW	1,349	18.53¢
Oklahoma	229 GWh	110.9 to 145.1 MW	1,789	13.37¢
Oregon	618 GWh	398.1 to 476.8 MW	1,413	15.31¢
Pennsylvania	974 GWh	811.8 to 984.0 MW	1,085	20.90¢
Rhode Island	282 GWh	453.2 to 224.4 MW	not usable	29.45¢
South Carolina	637 GWh	378.1 to 400.2 MW	1,637	16.04¢
South Dakota	7 GWh	3.8 to 5.4 MW	1,522	14.33¢
Tennessee	86 GWh	53.5 to 58.6 MW	1,534	13.90¢
Texas	4,956 GWh	2,803.0 to 3,072.0 MW	1,687	16.11¢
Utah	995 GWh	522.1 to 586.3 MW	1,795	13.17¢
Vermont	245 GWh	174.4 to 185.7 MW	1,361	23.98¢
Virginia	1,044 GWh	592.8 to 690.1 MW	1,628	16.69¢
Washington	634 GWh	430.7 to 503.6 MW	1,357	14.35¢
West Virginia	61 GWh	35.7 to 44.8 MW	1,516	15.42¢
Wisconsin	369 GWh	215.2 to 271.7 MW	1,516	18.99¢
Wyoming	33 GWh	17.4 to 21.7 MW	1,688	13.88¢
U.S. Total	83,918 GWh	47,774.7 to 53,228.1 MW	1,662	18.16¢

Rhode Island's line is printed and not used. Its capacity in the same EIA table halves in one year, from 453.2 MW to 224.4 MW, which gives 832 kWh per kW against 1,360 to 1,470 in the neighbouring New England states. That looks like a revision in the capacity series, not a sunless state, and the calculator falls back to the national figure for it.

These are fleet averages. A new, unshaded, south-facing array will usually do better than the average of everything already on roofs, so the calculator's system size errs large.

The tax credit in the price guide ended with 2025

HomeAdvisor's solar installation guide, updated June 19, 2026, prints a column of system costs after the federal credit, and says:

For systems installed in tax years 2022 to 2032, homeowners can claim up to 30% of the eligible system and installation costs.

The Internal Revenue Service, on a page updated July 4, 2026:

The credit is not available for any property placed in service after December 31, 2025.

So a homeowner reading the guide in 2026 is shown a price 30 per cent below what they can get. The price table on this page leaves that column out.

The same table does not follow its own arithmetic. Every row is $2,500 to $3,500 per kilowatt except one. The 8 kW row starts at $17,600 instead of $20,000, and the 7 kW row prints the same $17,500 to $24,500 with and without the credit.

And it is below the federal lab's range. Lawrence Berkeley National Laboratory's Tracking the Sun puts the 20th to 80th percentile of residential systems installed in 2023 at $3.2/W - $5.5/W (residential), against the guide's $2.50 to $3.50 per watt.

What the size does not account for

Shade and orientation. The state figure averages every system; your roof may be better or worse. A site assessment or a modelling tool tuned to your roof's tilt and direction replaces this figure for a design.

Export rules. Covering 100 per cent of annual use does not mean zero bills: much generation happens when the house is using little, and utilities credit exported power at rates set locally.

Growth in use. An electric car or a heat pump adds thousands of kWh a year. The share box goes above 100 per cent for that reason.

The sources, and why not PVWatts

Read 2026-09-13.

Electric Power Annual 2024, Table 3.21, Net generation from solar photovoltaic by state by sector, U.S. Energy Information Administration, released October 16, 2025. Estimated small-scale generation by state, 2024 and 2023, thousand MWh.

Electric Power Annual 2024, Table 4.7.B, Net summer capacity using renewable sources by state, U.S. Energy Information Administration, released October 16, 2025. Estimated small-scale solar photovoltaic capacity by state, 2024 and 2023, MW.

Electric Power Monthly, Table 5.6.B, Average price of electricity by state, U.S. Energy Information Administration, released August 26, 2026. Residential cents per kWh, year to date through June 2026.

More than half of small-scale photovoltaic generation comes from residential rooftops, U.S. Energy Information Administration, Today in Energy, June 1, 2017. Explains that small-scale generation is estimated, not metered.

Residential Clean Energy Credit, Internal Revenue Service, page last reviewed or updated July 4, 2026. Credit not available for property placed in service after December 31, 2025.

Tracking the Sun, 2024 Edition, Barbose, Darghouth, O'Shaughnessy and Forrester, Lawrence Berkeley National Laboratory, August 2024. 20th to 80th percentile installed price bands for systems installed in 2023.

NREL's PVWatts models a specific array at a specific tilt and azimuth, and would be the better tool for a design. Its servers could not be reached when this page was built, so the page uses what EIA measured the existing fleet to produce instead, and says so. Neither replaces a site assessment for shade.

Frequently asked questions

How many solar panels do I need?: Divide your annual kWh by your state's yield per kW, then by the panel's rating. In Arizona, 10,800 kWh needs about 5.5 kW, fourteen 400 W panels. In Washington the same use needs about 8 kW.
How much electricity does a kW of solar produce?: Nationally, EIA's 2024 estimates for small-scale solar work out to about 1,660 kWh per kW per year. The highest states, New Mexico, Nevada and Arizona, are near 2,000; Pennsylvania and Alaska are between 1,040 and 1,090.
Is the solar tax credit still available?: The IRS says the Residential Clean Energy Credit is not available for property placed in service after December 31, 2025. Some price guides updated in 2026 still show costs after a 30 per cent credit.
How much does a solar system cost?: HomeAdvisor's June 2026 guide gives $2.50 to $3.50 per watt installed, about $15,000 to $21,000 for 6 kW before incentives. Lawrence Berkeley National Laboratory's Tracking the Sun puts most residential systems installed in 2023 at $3.20 to $5.50 per watt.
Why is Rhode Island not used?: EIA's small-scale solar capacity for Rhode Island falls from 453.2 MW to 224.4 MW between the end of 2023 and the end of 2024 in the same table, which makes the per-kW figure 832, far below neighbouring states. The calculator uses the national figure instead.
Is EIA's solar generation measured?: No. EIA says utilities do not necessarily know how much rooftop PV generates, so it estimates small-scale generation from the data it collects from utilities and third-party owners.
What size wire for solar panels?: Wire size depends on the circuit's current, termination rating and conditions, not on the panels as such. The wire size calculator applies the residential code's ampacity rules.
How long do solar panels take to pay back?: Divide the installed cost by the annual value. At $2.50 to $3.50 per watt, a 5.5 kW Arizona system saving about $1,670 a year takes roughly 8 to 12 years before any change in electricity prices or export credit.

Check these numbers yourself

Electric Power Annual 2024, Table 3.21U.S. Energy Information Administration, released October 16, 2025, read 2026-09-13. Estimated small-scale solar generation by state.
Electric Power Annual 2024, Table 4.7.BEIA, released October 16, 2025, read 2026-09-13. Estimated small-scale solar capacity by state, 2023 and 2024.
Electric Power Monthly, Table 5.6.BEIA, released August 26, 2026, read 2026-09-13. Residential price by state, 2026 to June.
Residential Clean Energy CreditInternal Revenue Service, updated 2026-07-04, read 2026-09-13.
Tracking the Sun, 2024 EditionLawrence Berkeley National Laboratory, August 2024, read 2026-09-13.
How Much Does Solar Panel Installation Cost?HomeAdvisor, updated 2026-06-19, read 2026-09-13.

How every figure here is verified: Sources & Method. Who builds this: About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-09-13. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

Yields are this page's division of EIA's 2024 estimates of small-scale solar generation and capacity, read on 13 September 2026. They are estimates of the existing fleet, not a model of your roof. Electricity prices are EIA's residential averages. Tax treatment is quoted from the IRS page as read; confirm with a tax professional. Prices are HomeAdvisor's and Lawrence Berkeley National Laboratory's, not this site's.