Energy requirement
For each device, daily energy is running watts multiplied by hours used and duty cycle. A refrigerator that draws 150 watts while its compressor runs does not normally draw 150 watts for all 24 hours, so the default applies a 35% duty cycle. Your appliance, room temperature, door openings, and age can change that substantially.
Battery capacity
We multiply daily energy by the selected outage duration, then account for inverter efficiency and the reserve you do not want to consume. The displayed result rounds upward to the nearest 100 watt-hours. Choose a commercial capacity above the result rather than treating the number as an exact product size.
Output and startup surge
Battery capacity and inverter output are different constraints. We add selected running loads for the continuous requirement and model the largest device starting while the others run. Motors and compressors may require several times their running power for a short period.
Evidence rules
- Published dimensions, capacity, output, warranty, and supported accessories can come from current manufacturer documentation.
- Runtime, noise, cold-weather behavior, standby drain, and transfer performance require sourced independent tests or our own documented measurements.
- Prices and promotions are dated because they change frequently.
- We do not say we tested a product unless we physically tested it under a described protocol.
Important limits
This tool is not electrical, medical, fire-safety, or food-safety advice. Confirm device labels and manuals. High-draw heating appliances can exhaust portable batteries quickly. Medical-device backup plans should be reviewed with the device provider and an appropriate professional.