Will plug-in solar pay off where you live?

Five quick answers. Real sun and electricity prices for your state. Every number is shown.

Where do you live?

State
Electricity price, 12¢46¢ per kWh
Closest city in California

· sun and weather for

Where would the panels go?

Mounting

Which way do they face?

Direction the panels face

The amber arc is the sun's path across the southern sky.

How much shade?

How much room, and which panels?

Panel size

Your estimate

saved a year
to pay back the kit

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Solar per month:
Panels
Size
Solar a year

Your numbers

Rate: your state's average until you type your own. Used at home: the rest goes to the grid and earns $0. Limit: 1,200 W in California; check your state. Price: an example; use the real one.

Sun: PVGIS (NSRDB satellite data). Prices: EIA, through July 2026. Updated October 9, 2026.

How the calculator works

  1. Panels that fitRailing length ÷ panel length, or free area ÷ panel area. Panel sizes are typical; check your datasheet.
  2. The legal limitNever more panel watts than the limit you set: 1,200 W by default, California's cap per home.
  3. Sun in your citySystem size × a year of output for 1 kW at that angle and direction, minus shade.
  4. What it's worthThe share you use at home × your rate. Power sent to the grid counts as $0.
  5. PaybackKit price ÷ savings a year, at today's rate.

Where the numbers come from

  • Sun: the European Commission's PVGIS model, run for one city per state (five in California), three angles and five directions, with the satellite solar data of the National Laboratory of the Rockies (formerly NREL) where it covers the city (ERA5 elsewhere, such as Alaska) and 14% losses for wiring, inverter and dirt.
  • Prices: the EIA's average residential price by state, year to date through July 2026. Your bill's rate is better, especially on a time-of-use plan.
  • Our assumptions: the shade levels (0%, 10%, 25%, 50%) and the 80% used at home are rough estimates, not measurements. Change them if you know better.

What changes the result most

  • Your rate: state averages run from about 12¢ to 46¢ per kWh, so the same panels can save three times as much.
  • Angle: panels upright on a railing make much less than the same panels tilted on a stand.
  • Shade: a shaded balcony can halve the output.
  • Price: a cheaper kit shortens payback more than anything else you control.

Check that plug-in solar is allowed where you live before you buy, and that the kit is certified as a whole system. New to it? Start with what plug-in solar is.

Before you buy

Sources

  1. Electric Power Monthly, Table 5.6.B: Average Price of Electricity to Ultimate Customers by End-Use Sector, by State, Year-to-Date (Official document, US Energy Information Administration, 2026)
  2. PVGIS: Photovoltaic Geographical Information System (Source, European Commission Joint Research Centre, 2026)
  3. National Solar Radiation Database (NSRDB) (Source, National Laboratory of the Rockies (formerly NREL), US Department of Energy, 2026)
  4. SB 868: Electricity: portable solar generation devices (status, chaptered text and digest) (Source, CalMatters Digital Democracy, 2026)

An estimate, not a quote: real output depends on your exact spot, weather and equipment. This tool is general information, not electrical or legal advice. Safety disclaimer