OffGridSage

Off-Grid Calculators

Free calculators for solar power, batteries, water storage and rainwater harvesting.

Planning an off-grid system starts with numbers: how much power you use, how much battery you need, how much water to store. These free calculators do the math for you and show exactly how each result was worked out, so you can check it and adjust it to your situation.

Solar System CalculatorList your appliances and get panel watts, battery size, charge controller and inverter.Open calculator Battery Bank CalculatorWork out capacity, how many batteries you need and how to wire them in series and parallel.Open calculator Emergency Water CalculatorHow much water your household should store, in gallons or liters, and in which containers.Open calculator Rainwater Harvest CalculatorHow much rain your roof can collect each year and what size tank fits it.Open calculator

How to use these tools

  1. Start with your energy use. The solar calculator adds up your appliances and gives your daily watt-hours — the number every other power decision depends on.
  2. Size your storage. Use the battery bank calculator with that daily figure to choose capacity, voltage and wiring.
  3. Secure your water. Work out your emergency water reserve, then see how much a rainwater system could add.

All results are estimates for planning. Always check equipment specifications and local codes, and use a licensed professional for electrical work where required. Found a problem or want another calculator? Tell us.