Power Station Outage Runtime Calculator
How long a portable power station will actually run something during an outage, after the conversion losses its advertised capacity ignores.
The Wh figure on the spec sheet, not the watts.
Or type your own below.
Runtime
8h 22m
Assumes LiFePO4 and includes the inverter conversion loss.
- Simple capacity divided by load
- 10.0 h
- Lost to conversion and reserve
- 16%
A fridge does not run continuously. Its compressor cycles, so it draws its rated watts only part of the time and will usually last longer than this figure suggests. Powering it in cycles stretches capacity further still.
Why you get less than the number on the box
A power station advertised at 1,000 watt-hours will not deliver 1,000 watt-hours to an appliance. Converting stored DC into household AC loses roughly 10 to 15% as heat, and a little capacity is held in reserve to protect the cells.
Expect around 85% of the rated figure to reach what you plug in. That is normal rather than a defect, but it is rarely prominent in the marketing.
A fridge is easier than it looks
A refrigerator does not run continuously. Its compressor cycles, typically a third to a half of the time, so a fridge rated 150 watts averages closer to 100 and uses roughly 1 to 2 kWh across a day.
You can stretch that considerably. A closed fridge holds its temperature for hours, so powering it for twenty minutes an hour is often enough during an outage and makes a given power station last much longer. Check the yearly kWh figure on the appliance energy label and divide by 365 for a better number than any estimate.
Heat is the wrong job for a battery
Space heaters, kettles, toasters, hair dryers, and coffee makers all draw 1,000 to 1,500 watts continuously. Even where the inverter can supply it, a 1,000 Wh station running a 1,500 W heater lasts about half an hour.
Resistive heating is the least efficient possible use of stored battery energy, and no portable unit is a realistic answer for it. If heat is what you need during an outage, the answer is fuel rather than batteries.
What a power station cannot do
It cannot run anything hardwired: furnaces, well pumps, sump pumps, central air, or hardwired lighting. If there is no plug, powering it means an electrician fitting a transfer switch, which is a different kind of installation with its own code requirements.
If that is what you need, work throughchoosing your backup power type before buying anything.