Choose your energy profile
Start with a common U.S. household scenario, then customize the appliances below.
Add appliances
Add common devices to your household estimate. Wattage values are editable.
| Appliance | Qty | Watts | Hrs/day | Use % ? | Backup | kWh/day |
|---|
How to fill this in: Watts = running power; Hrs/day = time switched on; Use % = percent of those hours actually drawing the stated watts (e.g., compressor cycles). “Backup” marks devices you want powered during outages. Check appliance labels or use a watt meter for better accuracy.
Set your backup goal
How long do you want your selected essential appliances to keep running?
Advanced settings · electricity rate & efficiency
How this calculator works
Designed for early-stage battery backup planning—not electrical installation approval.
How do you calculate daily electricity usage?
For each appliance: quantity × running watts × hours per day × active-use percentage ÷ 1,000. The result is kWh/day. Household totals include all appliances in your list; backup totals include only appliances switched to “Backup.”
Why are battery capacity (Wh) and AC output (W) different?
Battery capacity (Wh or kWh) determines how long a system can run; AC output (W) determines which and how many appliances can operate simultaneously. A battery might have enough energy to run a window AC for hours but not enough AC output to start it.
Can I run a 240V central AC or well pump?
Choose a system with supported 120/240V output and the correct connectors or transfer equipment. Compressor starting surge, branch-circuit limits and professional installation still require verification. Never backfeed household circuits through a wall outlet.
Are electricity costs and recommended backup hours guaranteed?
No. Device labels, seasonal cooling demand, duty cycles, inverter standby consumption, temperatures, battery aging and actual load scheduling all change the outcome. Local utility pricing may have fixed charges and time-of-use tariffs that this simple energy-only estimate does not include.