Is plug-in solar legal in your state?

Yearly kWh = panel watts ÷ 1,000 × the state's yearly output per kW of panels.
Yearly savings = yearly kWh × share used at home × your price.
Payback = kit cost ÷ yearly savings.

Share used at home. "Best case" (100%) assumes you use every kilowatt-hour yourself. "Typical" (69%) comes from HTW Berlin's Stecker-Solar-Simulator. For an 800 W system with no battery, it modelled 56% for a home using 2,100 kWh a year, 69% for a home using 3,000 kWh a year, 88% for a home using 5,000 kWh a year. We use the 3,000 kWh case because it is well below every US state's average household use (EIA). The model uses German weather and household patterns and vertical panels, so treat it as a guide. HTW simulator.

Solar output comes from NREL (National Laboratory of the Rockies) PVWatts v8, typical meteorological year weather, run for each state capital with 14% system losses, panels at 20° facing south, and for vertical railing panels (90°, facing south). Real balconies face other directions, get shade, and are often limited by the inverter, so your output may be lower. Railing vs tilted panels by state.

Default prices are EIA's residential averages for September 2025 – August 2026 (12 months). We assume no payment for power sent to the grid, no incentives, and no price changes. Where a figure is missing, we show no estimate rather than guess.