Solar Panel Calculator

Primary output 7.43 kW · 19 panels

Enter your yearly electricity use, average peak sun hours, and panel wattage to size a basic home solar array. Open Advanced for monthly bills, loss/cost assumptions, or an existing-system generation estimate.

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Start with annual electricity use to size a new system, or switch to estimate output from an existing system.

Enter your electricity use for the selected period. A recent 12-month utility total is best.
Average daily peak sun hours for your location. Many U.S. homes fall between about 3.5 and 5.5 hours/day.
Nameplate DC wattage of one panel.
Advanced options
The calculator normalizes daily or monthly entries to a yearly kWh total before sizing the array.
Use the DC nameplate size of an array you already have or are evaluating.
The share of your annual electricity use you want solar to cover.
Combined real-world losses. NREL PVWatts commonly uses 14% as a default loss setting.
Physical footprint of one panel, used to estimate total roof area.
Your blended retail electricity rate. The 2024 U.S. residential average was 16.48 cents/kWh.
All-in installed price before incentives. Used for the cost and simple-payback outputs.
Answer 7.43 kW · 19 panels
System size 7.43 kW
Number of panels 19 panels
Required roof area 37.05 m² (399 ft²)
Estimated annual generation 10,500 kWh/yr
Show calculation details
Estimated annual savings $1,730.40/yr
Estimated installed cost $22,300.10
Simple payback period 12.9 years