Pre-filled with a typical essential-circuit load (fridge, some lighting, wifi, occasional pump draw) for 5 days of backup — adjust to match your actual circuits.
This covers steady average load only — add extra margin for anything that cycles on with a high surge draw, like a well pump or refrigerator compressor restart, checked separately against your inverter's surge rating.
Longer outages need proportionally more battery capacity — but real-world load, not this page's reference estimate, is what actually determines your number. Add up your specific essential circuits with the battery size calculator for a precise total, then apply your target outage duration here for the final capacity. If solar recharging is part of your plan rather than battery alone, factor that in with the off-grid system calculator's battery-plus-solar approach.
It's a reasonable reference for a refrigerator, some lighting and outlets, and networking equipment — but every home differs, especially if a well pump, sump pump, or medical equipment is part of your essential list. Adjust the field above to match your actual circuits for an accurate number.
Average load determines total energy (kWh) needed for the duration, but peak/surge load determines whether your inverter can actually start high-draw appliances — check both separately, since sizing only for average load can leave a battery that runs out of surge capacity even with plenty of energy left.