How to size a solar system for your home

Sizing solar comes down to matching production to your electricity use. You don't need to do the math perfectly — an installer will — but understanding it helps you sanity-check any proposal.

Step 1: Find your annual usage

Look at your electric bills for your yearly total in kilowatt-hours (kWh). Most utilities show a 12-month history. This is your target — how much energy you want solar to cover.

Step 2: Account for your local sun

The same panel produces more in Arizona than in Ohio. Solar output depends on “peak sun hours” for your area — a measure installers use to translate system size (kW) into expected annual production (kWh).

Step 3: Estimate system size

Roughly: annual kWh you want to offset ÷ (local production factor) = system size in kW. A typical home lands somewhere around 5–12 kW, but yours could be smaller or larger depending on usage and roof space.

Don't forget future loads

Planning an EV or heat pump? Size for that added demand now — it's cheaper than expanding later.

Tip: oversizing wastes money where net metering is weak; undersizing leaves savings on the table. Aim to cover the share of usage that pencils out under your net-metering rules.

Related: costs & savings · how solar works