The battery decides how long you stay powered. Size it to the hours of backup you actually want — no more, no less.
Start from daily energy
Take your daily consumption in kWh and the number of backup hours you want. The energy you need to store is roughly your average hourly use times those hours.
Account for usable depth
You can't drain a battery to zero. Divide the energy you need by the usable depth of discharge — about 90% for lithium, 50% for tubular — to get the nominal capacity to buy.
Ready to put it to work?
Use the free audit to apply what you've learned and size a system for your exact load.