The tool shed
Calculate. Don't guess.
Every calculator below runs entirely in your browser — nothing you type leaves your device. Each one publishes the formulas it uses so you can check the math yourself.
Solar Sizing Calculator
Size a complete off-grid solar system — panel array, battery bank, charge controller and inverter — from your real daily energy use and location.
“How many panels and batteries do I actually need?”
Open toolBattery & Runtime Calculator
Find out how long a battery bank will run a given load — or how much battery you need to run your gear for a set number of hours.
“How long will my battery last, and what size do I need?”
Open toolRainwater Harvesting Calculator
Estimate how much water your roof can collect from local rainfall, and whether your tank and demand line up across the dry season.
“How much rain can I catch, and is my tank big enough?”
Open toolWater Demand Estimator
Estimate your household's daily and annual water needs across drinking, cooking, washing, toilet, garden and livestock.
“How much water do I actually need each day?”
Open toolFood Storage Calculator
Plan a long-term food store: how many calories, and how much of each staple, to feed your household for a chosen number of months.
“How much food should I store, and of what?”
Open toolA note on accuracy
These tools use standard engineering estimates and sensible safety margins. They are for planning and education, not for final engineered designs. Always have a qualified electrician, engineer or installer verify any system that involves mains voltage, structural loading, or drinking-water safety before you build.