Off-Grid Load Calculator (Daily Watt-Hours)
Add up every appliance's watts, run-hours, and quantity into a total daily watt-hour load, then get a suggested solar array size to replace it.
array = 1.8 kWh ÷ (4.5 × 0.8) = 0.5 kW
Every off-grid design starts with one honest number: how many watt-hours you burn in a day. This worksheet builds it appliance by appliance. For each item you enter its running watts, how many hours a day it runs, and how many of them you have. Watts times hours times quantity gives that appliance's daily watt-hours, and the tool sums every row into a total. Add or remove rows until the list matches how you actually live.
That daily total drives the rest of the system. Divide by `1,000` and you have your daily kWh, the figure the battery-bank and inverter tools ask for. The worksheet also suggests a solar array size using the standard identity: array kW equals daily kWh divided by your local peak sun-hours times a derate factor. Peak sun-hours run from about `3.5` in cloudy regions to `6` in the desert Southwest, and the `0.8` derate trims roughly `20%` for inverter, wiring, and temperature losses.
Be honest and slightly generous. Phantom standby draws, a refrigerator's real duty cycle, and seasonal swings all push the true number up, so it is safer to overestimate a load than to run out of power on the fifth cloudy day.
LED lights `12 W` × `5 h` × `5` = `300 Wh`
TV `100 W` × `3 h` × `1` = `300 Wh`
total = `1,800 Wh/day` (`1.8 kWh`)
array = `1.8 kWh` ÷ (`4.5` sun-hours × `0.8`) = `0.5 kW`