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.
Need to check a load before an outage? Use the backup power calculators for cited wattage estimates and the formulas behind them.
Guides
What Can a 1000Wh Power Station Run During an Outage?
A 1000 Wh station estimates to 12 hours on a 70 W refrigerator load. Compare that math with starting watts, published station specs, and loads that need 240 V.
How Long Will a Power Station Run a Refrigerator?
A 1000 Wh station estimates to 12 hours on EIA’s 70 W fridge average or 21 hours on a 41 W ENERGY STAR top-freezer estimate. Starting watts need a separate check.
Backup Power for Renters and Apartments
A 1000 Wh battery estimates to 12 hours on a 70 W fridge load. Plug appliances into it, never backfeed a wall outlet, and keep fuel generators outside.
Sizing a Power Station for a CPAP Overnight
Worked estimates for an overnight CPAP backup using ResMed’s published AirSense 11 wattages, a simple watt-hour formula, and the limits of a 500–1000 Wh portable power station. Not medical advice and not a lab test.
How Much Solar to Recharge a Power Station in a Day
A cautious way to estimate how much portable solar you need to refill a power station in a day, using NREL’s sun-hour definition, a station’s published solar-input cap, and PVWatts for your own location. Not a field test.
Can a Power Station Run a Window AC or a Space Heater?
Why a 1 kWh-class power station can fail a window air conditioner or space heater in two different ways: inverter surge and continuous limits, plus battery energy that lasts only minutes. Honda published wattages and a simple runtime formula, not a lab test.
Can a Power Station Run a Sump Pump?
A 120 V station cannot run the 240 V sump pumps in Honda’s table. At the table’s 800 W running load, a compatible 1000 Wh station estimates to 64 minutes of continuous pump time.
Generator vs Power Station for Apartments
A 1000 Wh battery estimates to about 12 hours on a 70 W refrigerator average, while a gasoline generator is not safe to run indoors. Compare the safety limits, load math, and apartment tradeoffs without treating this as a product test.
How Long Will a Power Station Run a Chest Freezer?
A 1000 Wh station estimates about 34 hours on a new ENERGY STAR chest freezer averaging 24.9 W. The estimate uses 218 kWh/year and a 0.85 planning factor, not a power-station test.
How Many Watts Does a Furnace Blower Need?
Honda’s 1/3 hp furnace-fan example needs 1,400 W to start and 700 W to run, with a 240 V flag. A compatible 1000 Wh supply estimates to 1.2 hours at that running load, not a whole-furnace test.
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.