Every calculator on SolarWattPro is listed here, grouped by topic. Each one opens inside a detailed guide that explains the formula behind it, shows worked examples and points out the mistakes people most often make, so you understand the answer as well as get it.
All the calculators are free, need no sign-up and run entirely in your browser. Nothing you type is sent to us or saved. They share the same formulas, so a battery size from one tool always agrees with the battery size in another. Peak sun hours come from our solar potential by country guide, and every result includes 20% real-world system losses.
Not sure where to start? The all-in-one calculator on our home page plans a complete system from your appliances or electricity bill. If you already know your system size, use the solar system output calculator. For a factory, shop, school, farm or farm irrigation pumps, use the business solar calculator.
Main calculators
Solar panels and production
How to get the most accurate answer
- Use your real numbers: the watts on your appliance labels, the kWh on your last 12 electricity bills, and the peak sun hours for your city rather than the country average if you know them.
- Size off-grid systems for your worst month, not the yearly average.
- Check the inverter and wiring calculators before buying parts. Undersized cables and inverters are the most common and most dangerous mistakes.
- Treat every result as a planning estimate and have a qualified installer confirm the final design.