Backup power, explained in hours and watts
Will it run — and for how long?
Will It Run Lab helps households in the United States, Canada, the United Kingdom, and Australia estimate what a portable power station can keep on during an outage. We use published manufacturer specifications and official energy-use data. We do not invent lab results, prices, or ratings.
Guides
Backup Power for Renters and Apartments
How to plan apartment and rental backup power with a portable power station — indoor-safe batteries versus generators, no backfeeding, lease and balcony constraints, and a realistic essential-load list.
How Long Will a Power Station Run a Refrigerator
Estimate refrigerator runtime from annual kWh, average watts, surge versus running watts, and a simple watt-hour formula — using ENERGY STAR, EIA, and manufacturer figures, not invented tests.
What Can a 1000Wh Power Station Run During an Outage
Use published capacities, inverter limits, and a simple watt-hour formula to see what a 1 kWh-class portable power station can and cannot run when the grid goes down.
A simple runtime estimate
For planning, a useful first estimate of how long a portable power station can run a load is:
Runtime (hours) ≈ battery capacity (Wh) × inverter efficiency ÷ load (W)
We use 0.85 as a conservative inverter-efficiency factor when a manufacturer does not publish one. That is a planning assumption, not a lab measurement. Some makers publish a similar figure: BLUETTI, for example, lists inverter efficiency of 85% for the AC180, and also subtracts depth of discharge and the station’s own standby draw.
Use this calculator for the simple form of the estimate. It runs in your browser and does not send any data.
This is not a test result. Real runtime also depends on depth of discharge, standby consumption, temperature, battery age, and whether the load cycles (a refrigerator) or runs continuously (a lamp). For surge versus running watts, see the article notes below: the inverter must cover the motor’s starting surge even if average watts look small.
How we work
Runtime is estimated as watt-hours × inverter efficiency ÷ load watts, with 0.85 as a conservative efficiency factor unless a manufacturer publishes its own. Refrigerator averages come from ENERGY STAR’s certified-model dataset and from the US Energy Information Administration’s Residential Energy Consumption Survey. Starting versus running watts come from published guides such as Honda’s wattage estimation table, and from nameplates. Read the about page for the full method and its limits.