Your daily energy budget
Estimates only. Defaults are illustrative placeholders – replace them with your devices' rated figures. Your entries stay in this browser.
How the maths works
- Daily energy (Wh) = Σ (watts × hours per day) for each appliance. For cycling appliances such as a compressor fridge, the "hours" are the time the compressor actually runs – the calculator uses a duty-cycle field for that.
- Battery size (Ah) = daily Wh × days of autonomy ÷ usable depth of discharge ÷ 12.8 V.
- Solar (W) = daily Wh ÷ peak-sun hours ÷ a system-loss factor (0.75 by default – heat, angle, controller and cable losses).
- DC-DC charger (A) = the current that would refill a day's energy during your typical daily driving time.
Typical inputs
The defaults are placeholders, not measurements: replace them with the watt figures printed on your devices or their manufacturer's spec sheets. For a compressor fridge, use the manufacturer's rated power and a realistic run-time share.
Electrical safety. 12 V systems carry high currents that can start fires; mains (120/230 V) wiring can kill. Fuse every positive cable at its source, size cables to the manufacturer's tables, and have your system designed or checked by a qualified auto-electrician. Mains wiring should be done by a qualified electrician.
Next steps: pick a lithium battery, a DC-DC charger and solar panels – and have the final design checked by a qualified auto-electrician.
Frequently asked questions
How accurate is this calculator?
It's a planning estimate. Appliances' real consumption varies with temperature, settings and usage. Use manufacturer figures where you have them, and leave a margin.
Why does the calculator assume 12.8 V?
12.8 V is the nominal voltage of a 4-cell LiFePO4 battery, the most common van house battery.
What does 'days of autonomy' mean?
How many days you want to run without any charging (cloudy, parked). More days = bigger battery.
Spotted an outdated spec? Tell us.