How to read your electricity bill for solar sizing

Updated October 2026

You do not need the price on your bill to size a solar system. You need the energy you used, shown in kilowatt-hours (kWh). Everything else follows from that number.

Step 1: find the kWh

Look for a line such as "energy used", "consumption" or "kWh". Some bills show a bar chart of the last 12 months. Take the monthly kWh, or better, the average of several months, because use changes with the seasons.

Step 2: turn it into daily use

Divide the monthly kWh by 30.4. Example: 450 kWh ÷ 30.4 = 14.8 kWh a day.

Step 3: turn daily use into array size

Divide by sun hours times 0.8 for typical losses. With 4.5 sun hours: 14.8 ÷ (4.5 × 0.8) = 4.1 kW.

Details that change the answer

• Summer peaks. If air conditioning doubles your summer use, decide whether to cover the peak or the average.
• Time-of-use pricing. If evening power costs more, a battery or a hybrid system may save more than extra panels.
• Future loads. An electric car or a heat pump can add several kWh a day.
• Credits and limits. Utilities differ on what they pay for exports, so check local rules.

Next step: enter your kWh in the calculator, or read how many solar panels you need.