Home solar cost and contracts

How Many Kilowatts of Solar Does a House Need?

Published · By the SolarPanelX editors · Prices and specs as of that date, from the pages under Sources

Summary

Start from your electricity use, not your roof. Add up a full year of kilowatt-hours from your bills, then model how much a kilowatt of panels produces at your address and size the array to cover the share you want. As a rough national benchmark, EnergySage says the typical home needs about 12 kW.

A year of bills

Usage swings with the seasons. DOE notes that past bills show how much power a home needs both annually and by season, which a single summer or winter bill can't tell you.

Output per kilowatt depends on the address

PVWatts estimates production for grid-connected systems from your location, DC system size, tilt, azimuth, and losses. It is run by the National Laboratory of the Rockies (NLR), the name DOE gave NREL on December 1, 2025. The default system loss is 14%, which bundles soiling, shading, wiring, connections, light-induced degradation, and several smaller factors. Try a few system sizes and keep the one whose annual estimate lands near your target.

Then count panels

Divide system watts by module watts. A 12 kW array built from 400 W modules is 30 panels. Whether 30 panels actually fit depends on roof shape, shade, and module dimensions.

Sources

  1. EnergySage — Solar Panel Cost in 2026 (updated June 30, 2026)
  2. U.S. Department of Energy — Walk Me Through It: A Step-By-Step Guide for Consumers Going Solar
  3. National Laboratory of the Rockies — PVWatts Calculator
  4. National Laboratory of the Rockies — History

We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.

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