How Much Does Plug-In Solar Really Save? The Math by State

Short answer: an 800 W plug-in solar kit, facing south with no shade, saves roughly $70 to $490 a year depending on where you live and how you mount it, if you use 80% of what it makes at home. On a stand tilted toward the sun it saves about $100 to $490; hung flat against a balcony railing, about $70 to $220. At an example price of $1,000 on a stand, that’s a payback of about 2 years in Honolulu, 3 in California and 4 to 5 in New England and New York, but 7 to 10 years where power is cheapest, and longer still on a railing.

The result comes down to five numbers: what you pay per kWh, how much sun your spot gets, how the panels are mounted, how much of the power you use as it’s made, and what the kit cost. The table below works them out for every state. Then change the ones that don’t match you.

The math in one line

Savings a year = kWh the panels make × share you use at home × your price per kWh.

• kWh the panels make come from solar models: for one city in each state (usually its largest city or metro area), we used the European Commission’s PVGIS, which runs on the US National Laboratory of the Rockies’ satellite solar data, with its default 14% of system losses.
• Share you use at home (self-consumption): we assume 80%. With most plug-in systems, power you send to the grid earns nothing, so only what you use at the moment it’s made lowers your bill. More on this below.
• Your price per kWh: the average residential price in your state from January to July 2026, from the EIA’s Electric Power Monthly.

The payback period is simply the kit’s price divided by the savings a year, the method the Department of Energy walks through. Existing plug-in models cost from about $300 to $2,200 depending on size, according to KQED. We use $1,000 as an example, not a price for any product: use the real price of the kit you’re looking at.

What 800 W saves in every state

800 W of panels facing south, no shade, 80% used at home. Railing means panels hung vertically (90°), as on a balcony railing or a wall; stand means panels tilted at 30°, as on a ground stand or a flat roof.

State (city)	Price, Jan–Jul 2026	Railing: kWh a year	Railing: saved a year	Stand: kWh a year	Stand: saved a year	Payback at $1,000 (stand / railing)
Alabama (Birmingham)	16.5¢	720	$95	1,160	$153	6.5 / 10.5 years
Alaska (Anchorage)	27.1¢	640	$138	770	$167	6.0 / 7.2 years
Arizona (Phoenix)	15.4¢	880	$108	1,450	$179	5.6 / 9.2 years
Arkansas (Little Rock)	13.6¢	720	$79	1,160	$126	7.9 / 12.7 years
California (Los Angeles)	33.2¢	820	$218	1,360	$363	2.8 / 4.6 years
California (San Diego)	33.2¢	760	$203	1,240	$329	3.0 / 4.9 years
California (San Francisco)	33.2¢	830	$222	1,330	$354	2.8 / 4.5 years
California (Sacramento)	33.2¢	820	$218	1,320	$350	2.9 / 4.6 years
California (Fresno)	33.2¢	790	$210	1,320	$350	2.9 / 4.8 years
Colorado (Denver)	16.7¢	890	$119	1,300	$174	5.7 / 8.4 years
Connecticut (Bridgeport)	28.0¢	740	$165	1,090	$244	4.1 / 6.1 years
Delaware (Wilmington)	17.9¢	730	$105	1,090	$155	6.4 / 9.6 years
District of Columbia (Washington)	24.7¢	730	$145	1,100	$216	4.6 / 6.9 years
Florida (Miami)	15.3¢	660	$81	1,240	$152	6.6 / 12.3 years
Georgia (Atlanta)	15.4¢	740	$91	1,190	$147	6.8 / 11.0 years
Hawaii (Honolulu)	46.3¢	600	$224	1,310	$487	2.1 / 4.5 years
Idaho (Boise)	13.0¢	810	$84	1,210	$125	8.0 / 11.9 years
Illinois (Chicago)	19.2¢	620	$96	970	$150	6.7 / 10.5 years
Indiana (Indianapolis)	17.0¢	680	$93	1,050	$144	7.0 / 10.7 years
Iowa (Des Moines)	14.2¢	770	$87	1,120	$127	7.9 / 11.5 years
Kansas (Wichita)	15.2¢	810	$99	1,240	$151	6.6 / 10.1 years
Kentucky (Louisville)	14.3¢	700	$80	1,090	$124	8.1 / 12.5 years
Louisiana (New Orleans)	13.3¢	700	$74	1,180	$126	7.9 / 13.5 years
Maine (Portland)	30.0¢	750	$179	1,060	$254	3.9 / 5.6 years
Maryland (Baltimore)	21.3¢	740	$126	1,100	$187	5.3 / 8.0 years
Massachusetts (Boston)	30.1¢	760	$183	1,090	$262	3.8 / 5.5 years
Michigan (Detroit)	21.5¢	670	$116	1,020	$176	5.7 / 8.6 years
Minnesota (Minneapolis)	16.2¢	760	$99	1,070	$139	7.2 / 10.1 years
Mississippi (Jackson)	15.2¢	710	$86	1,170	$142	7.0 / 11.6 years
Missouri (Kansas City)	14.0¢	770	$86	1,150	$128	7.8 / 11.6 years
Montana (Billings)	13.9¢	780	$87	1,100	$123	8.1 / 11.5 years
Nebraska (Omaha)	12.9¢	790	$81	1,140	$118	8.5 / 12.3 years
Nevada (Las Vegas)	13.5¢	920	$100	1,450	$157	6.4 / 10.0 years
New Hampshire (Manchester)	26.8¢	740	$158	1,050	$224	4.5 / 6.3 years
New Jersey (Newark)	24.0¢	740	$142	1,090	$209	4.8 / 7.0 years
New Mexico (Albuquerque)	15.1¢	930	$113	1,480	$179	5.6 / 8.9 years
New York (New York City)	29.4¢	720	$169	1,050	$247	4.0 / 5.9 years
North Carolina (Charlotte)	14.9¢	750	$89	1,160	$139	7.2 / 11.2 years
North Dakota (Fargo)	12.4¢	730	$73	1,020	$101	9.9 / 13.8 years
Ohio (Columbus)	18.7¢	670	$100	1,030	$155	6.5 / 10.0 years
Oklahoma (Oklahoma City)	13.6¢	800	$87	1,260	$137	7.3 / 11.5 years
Oregon (Portland)	15.4¢	610	$75	910	$112	8.9 / 13.3 years
Pennsylvania (Philadelphia)	21.0¢	730	$124	1,090	$183	5.5 / 8.1 years
Rhode Island (Providence)	29.2¢	750	$176	1,080	$252	4.0 / 5.7 years
South Carolina (Charleston)	15.9¢	740	$94	1,210	$155	6.5 / 10.6 years
South Dakota (Sioux Falls)	14.5¢	800	$92	1,130	$131	7.6 / 10.8 years
Tennessee (Nashville)	13.9¢	690	$77	1,090	$120	8.3 / 13.1 years
Texas (Houston)	16.1¢	670	$86	1,160	$149	6.7 / 11.7 years
Utah (Salt Lake City)	13.2¢	800	$84	1,220	$129	7.8 / 11.8 years
Vermont (Burlington)	23.9¢	680	$130	980	$188	5.3 / 7.7 years
Virginia (Virginia Beach)	16.8¢	750	$101	1,160	$157	6.4 / 9.9 years
Washington (Seattle)	14.4¢	630	$72	920	$106	9.4 / 13.8 years
West Virginia (Charleston)	15.5¢	650	$80	1,020	$126	8.0 / 12.4 years
Wisconsin (Milwaukee)	19.0¢	720	$110	1,070	$163	6.1 / 9.1 years
Wyoming (Cheyenne)	13.9¢	890	$99	1,290	$143	7.0 / 10.1 years

Read it as a starting point, not a quote. One city stands for each state (five for California), and the price is the state average: your utility, your rate plan and your city’s weather can each move the result. Change the numbers to yours in the plug-in solar calculator, which uses the same data.

Why the mounting matters as much as the state

A panel flat against a railing gets far less sun over a year than one tilted toward it. In our numbers, a railing makes between 46% (Honolulu) and 83% (Anchorage) of what the same panels make on a 30° stand. It does worst where the sun stands high most of the year, as in Hawaii, Florida and along the Gulf Coast, and best in the far north. In Birmingham, Alabama, 800 W makes about 720 kWh a year on a railing and 1,160 kWh on a stand.

Models disagree more on vertical panels than tilted ones. As a check, we ran five cities through the DOE lab’s PVWatts calculator with the same 14% losses: for a 30° stand it came within about 4% of PVGIS, but for a vertical railing it gave 3% to 9% less (Birmingham: 813 kWh per kW against PVGIS’s 896). If your only spot is a railing, plan with the lower number.

Direction counts too: facing east or west instead of south lowers output, and shade from a building, a tree or the balcony above can cut it sharply. The calculator lets you set both.

How much of the power you use decides the savings

A plug-in system feeds your home first. Whatever your home isn’t using at that moment flows out to the grid, and with most plug-in systems it earns you nothing: they are usually left out of net metering. So the share you use on the spot is one of the biggest numbers in the math. For an 800 W stand at the state’s average price:

City	Use 100%	Use 80%	Use 50%
Honolulu, Hawaii (46.3¢)	$608 a year	$487 a year	$304 a year
Los Angeles, California (33.2¢)	$454 a year	$363 a year	$227 a year
Birmingham, Alabama (16.5¢)	$191 a year	$153 a year	$96 a year
Seattle, Washington (14.4¢)	$133 a year	$106 a year	$66 a year

You use more of it when something is running while the sun is out: a fridge (see how many watts a refrigerator uses), a router, a home office, laundry or a dishwasher run at midday. If nobody is home during the day and little runs then, your share may be well below 80%, and a smaller system may make more sense than a bigger one.

When it doesn’t pay off

Be honest with yourself about these, because they stack:

• Cheap power. Below about 15¢ per kWh, an 800 W stand saves less than $150 a year in most cities, so a $1,000 kit takes 7 years or more to pay back.
• A railing or a shaded spot. On a railing, payback in those same states is about 10 years or more, and shade adds to it.
• Little use during the day. At 50% used at home, every saving above drops by more than a third.
• A fixed monthly charge. The EIA’s average price spreads fixed charges over every kWh, but solar only cuts the part of your bill that depends on kWh. Check your bill for the price per kWh you actually pay, delivery included.

If all of these describe you, a plug-in kit is unlikely to pay for itself on savings alone. It can still make sense for other reasons, but go in knowing that.

How much of your bill can it cover?

Less than many people expect. The average US home used 863 kWh a month in 2024, or about 10,400 kWh a year (EIA, Table 5A). An 800 W stand makes roughly 800 to 1,500 kWh a year in our cities, around a tenth of that. A small apartment that uses less will see a bigger share. Compare your own use with your state’s in our guide to the average electric bill by state.

Before you buy

Savings only count if the system is allowed where you live and on your building. Check your state’s rules first in our guide to plug-in solar laws by state: in states without a plug-in law, your utility’s rules for rooftop solar apply. If you rent, ask your landlord; if you own in an HOA, read its rules. New to all this? Start with what plug-in solar is.

How we did the math

• Solar output: PVGIS (version 5.2, US satellite data from the National Laboratory of the Rockies’ NSRDB; version 5.3 with ERA5 data for Anchorage), 1 kW of panels, 14% losses, facing south, at 90° (railing) and 30° (stand), for one city per state and five in California. Retrieved October 9, 2026 for our calculator, scaled to 800 W. PVWatts version 8 spot check on October 22, 2026 for Birmingham, Los Angeles, New York City, Seattle and Phoenix.
• Prices: EIA Electric Power Monthly Table 5.6.B, residential average, year to date through July 2026.
• Assumptions: 800 W, south, no shade, 80% used at home, exports worth $0, a $1,000 example price, no incentives, no change in prices. Rising prices would shorten payback: the DOE’s guide notes that the faster electricity prices rise, the shorter the payback.
• What it can’t tell you: your own rate plan, your own shading, how much you use at midday, or how long a given kit will last. Data checked October 22, 2026.