Solar Calculator

Estimate the size, cost, savings and battery backup for a system at your address.

A close-up photograph of a residential off-grid photovoltaic array in rural Homs, Syria. The setup consists of 4
Photo: Hayan Alhasan, CC BY-SA 4.0, via Wikimedia Commons

Enter your numbers below for a quick, honest estimate. Everything updates as you type. Results are planning figures, not a quote.

Solar system size and savings

On your electric bill. Use a 12 month average.
Approximate annual averages. Fills in sun hours.
For a precise figure use NREL PVWatts or Global Solar Atlas.
Any currency. Results use the same currency.
Before incentives. Take it from your quotes.
Fridge, lights, internet, a fan or well pump.
System size
Panel count
Estimated production
Cost before incentives
Bill savings if fully credited
Simple payback
Approximate panel area
Battery for your backup goal

Assumes a performance ratio of 80 percent (wiring, heat, dust and inverter losses) and that every kWh offsets a kWh you would have bought. Under net billing or export limits, exported energy may earn less, so savings can be lower. Battery size allows for 90 percent usable depth and 95 percent inverter efficiency.

Getting a more precise estimate

For the most accurate production figures for your exact address, roof angle and direction, use these free tools:

  • PVWatts from the U.S. National Renewable Energy Laboratory, which works for locations across the Americas.
  • Global Solar Atlas from the World Bank, with solar resource maps for every country.
  • Google Project Sunroof and similar roof mapping tools where available.

Then compare your estimate with installer quotes using the checklist in Buying Solar Wisely, and subtract any rebates or credits on the incentives page.

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