About SolarCalcLab
Free solar and electrical calculators that show their working.
SolarCalcLab is a free library of solar and electrical calculators for homeowners, DIY installers and electricians. Every tool shows the formula it uses, the inputs it assumes and the sources behind its data, so you can check the answer instead of trusting a black box.
What we build
We build calculators for the questions people ask before and after going solar: how big a system to buy, how many panels fit a bill, how long a battery will last, which wire size keeps voltage drop in check and whether the numbers pay off. Each calculator sits next to a plain-English guide that explains the result.
How we work
- Open formulas. The equation and a worked example sit under every result.
- Real data. Location-based tools use sunlight data from PVGIS and NREL, and cost tools use published tariffs from regulators and statistics agencies.
- Sources and dates. Every tool and guide lists its sources and the date it was last checked.
- No sign-ups. You never need an account, and we do not ask for your phone number to show a result.
Read more in How we calculate, our editorial policy and our data sources.
Who it is for
We write for readers in the United States first, with country settings and notes for the United Kingdom, Australia and Europe where rules and voltages differ.
Contact
Questions, corrections or partnership ideas: use our contact page. If you spot a mistake in a result, please use report an error so we can fix it quickly.