OffGridVolts is a free collection of calculators for low-voltage and off-grid electrical systems: leisure batteries, solar panels, charge controllers, inverters, cables, fuses and small wind turbines. It's aimed at people fitting out campervans, RVs and motorhomes, boats, cabins, sheds and workshops, in the UK, the US and anywhere else.
Who runs it
The site is run by a UK electronics hobbyist and licensed radio amateur with years of hands-on experience of 12 V wiring, battery systems, wind and automotive electrics. The calculators are the ones we wished existed when planning our own systems: quick, honest about their assumptions, and usable in either metric or imperial units.
How the calculators work
- Every calculator shows the formula it uses, so you can check the working yourself.
- Default values are typical, conservative figures. Change them to match your own equipment's datasheet.
- Everything runs in your browser. Nothing you type is sent to us or stored.
Corrections
If you spot an error or have an idea for a new calculator, please get in touch. Corrections are fixed quickly.
Safety
Results are estimates for planning. Batteries can deliver very high currents, and mains (AC) wiring can kill. Follow the manufacturer's instructions and your local wiring regulations, and use a qualified electrician for anything connected to mains or hook-up supplies. See our terms and disclaimer.