Solar power
How much solar
do you actually need?
Turn your power bill and roof into a first estimate of system size, output, and payback.
Start here
Most people start with these
Solar system size calculator
Estimate the solar system capacity needed from daily electricity use, local solar resource, roof area, tilt, and orientation/shading assumptions.
Open calculator ↗Solar panel count calculator
Estimate how many panels are needed for a target solar system size.
Open calculator ↗Solar payback calculator
Estimate simple payback from system cost and annual energy savings.
Open calculator ↗All tools
5 solar calculators
How to plan a solar system
Solar output depends on sun hours where you live, roof orientation and shade, and system losses. Start with the system size your daily kWh needs, check panel count and annual generation, then test payback using the price you actually pay per kWh from your bill.
Payback is sensitive to electricity prices and incentives, so treat the first result as a conversation starter for quotes — see electricity prices by country for a realistic rate. Planning note: these are estimates, not engineering, installation, vehicle, or financial guarantees. Verify specifications and local rules with a qualified installer.