Bill-based solar calculator
How many solar panels do you need based on your electric bill?
A $150 monthly energy charge at 18.4¢ per kWh represents about 815 kWh of electricity. With 400-watt panels, five peak sun hours and 20% system losses, the planning estimate is 17 solar panels.
Reviewed July 24, 2026
Free bill-to-panel calculator
Estimate panels from your monthly electric bill
Change the electricity rate to the exact cents per kWh shown on your bill. If your bill lists monthly kWh, use the main calculator instead.
Solar panel estimates by monthly electric bill
The examples below use an electricity price of 18.4¢ per kWh, the U.S. residential average reported by the Energy Information Administration for May 2026. They also assume 400-watt panels, five peak sun hours, 20% system losses and 100% electricity offset.
| Monthly energy charge | Estimated monthly use | Estimated panels | System size |
|---|---|---|---|
| $50 | 272 kWh | 6 | 2.4 kW |
| $100 | 543 kWh | 12 | 4.8 kW |
| $150 | 815 kWh | 17 | 6.8 kW |
| $200 | 1,087 kWh | 23 | 9.2 kW |
| $250 | 1,359 kWh | 28 | 11.2 kW |
| $300 | 1,630 kWh | 34 | 13.6 kW |
These are formula outputs, not promises that a system will fit your roof or eliminate the entire bill.
Why the electricity rate matters
A $150 bill does not represent the same electricity consumption everywhere. At a lower price per kWh, that money buys more electricity, so more solar production is needed. At a higher rate, it buys less electricity, so the panel estimate is smaller.
| Rate for a $150 bill | Estimated use | Estimated 400 W panels |
|---|---|---|
| 14¢/kWh | 1,071 kWh/month | 23 |
| 18.4¢/kWh | 815 kWh/month | 17 |
| 30¢/kWh | 500 kWh/month | 11 |
How the bill calculator works
First, the calculator estimates electricity use from the portion of the bill tied to energy. Then it converts that monthly use into an annual solar target and divides by the estimated annual output of one panel.
What part of the bill should you enter?
- Best: use the average monthly kWh from twelve bills in the main calculator.
- Next best: enter the average monthly energy charge and your exact electricity price.
- Subtract fixed charges: customer fees, minimum bills, taxes and some demand charges may remain even after adding solar.
- Do not use only the highest bill: seasonal heating or cooling can make one month unrepresentative.
Frequently asked questions
How many solar panels do I need for a $100 electric bill?
At 18.4 cents per kWh, a $100 energy charge represents about 543 kWh per month. Under this guide's assumptions—400-watt panels, five peak sun hours and 20% system losses—that is approximately 12 panels.
How many solar panels do I need for a $200 electric bill?
At 18.4 cents per kWh, a $200 energy charge represents about 1,087 kWh per month. Under the guide assumptions, that is approximately 23 400-watt panels.
Can I calculate solar panels from the dollar amount alone?
Only approximately. The same dollar bill can represent very different electricity use because rates, taxes and fixed charges vary. Monthly kWh from twelve bills is the stronger input.
Should I use my highest electric bill or my average bill?
Use the average of twelve months whenever possible. A single summer or winter bill can overstate the annual system size because heating and cooling loads are seasonal.