How Many Solar Panels Do I Need? A Simple 2026 Guide

The number of solar panels you need depends on three things: how much electricity you use, how much sun your roof gets, and how powerful the panels are. Get those three numbers and the math is quick.

Start with annual usage. Add up the kilowatt-hours (kWh) from your last twelve utility bills. The US average home uses about 10,800 kWh per year, but yours could be far higher with electric heat, air conditioning, or an EV.

Next, find your production ratio — the kWh a 1 kW system makes per year where you live. This ranges from about 1,150 in the cloudy Northeast to over 1,700 in the desert Southwest. Our address-based estimator pulls the exact figure from NREL PVWatts.

Divide usage by the production ratio to get system size. For 10,800 kWh and a 1,400 ratio, that is about 7.7 kW. At roughly 400 watts per panel, that is about 20 panels needing around 420 square feet of roof.

Finally, adjust for your goals. If your state has strong net metering, sizing to 100% of usage usually pays off. If exports are credited at a low rate, consider sizing to your daytime load and adding a battery instead.