How big a power station do you need for a power cut?
List what must keep running, add up watt hours, allow for losses, and check the output power. A simple method with a worked example.
Start with what must keep running
Write down the devices you really need during a cut and for how many hours: the fridge, the internet router, phone charging, a few lamps, perhaps the circulation pump of the heating. For each one, multiply its power in watts by the hours of use. For a fridge, use the annual consumption on its energy label: a fridge labelled 150 kWh per year uses about 0.4 kWh, or 400 Wh, per day.
A worked example
For one day: fridge 400 Wh, router at 10 W for 24 hours 240 Wh, two lamps at 8 W for 5 hours 80 Wh, phones and a laptop 100 Wh. Together about 820 Wh. Now allow for losses: the inverter itself draws power, and the usable energy is lower than the rated capacity. In Stiftung Warentest's 2023 test, one model delivered about 84 percent of its rating. Planning with about a quarter more is a reasonable margin, so roughly 1,000 to 1,100 Wh for this day.
Check the output power too
Capacity tells you how long, output power tells you what. The station's continuous output must be higher than all devices running at once, and motors such as a fridge compressor need a short peak when they start, so check the surge rating as well. Heaters, kettles and electric cookers draw so much that they empty a portable station in minutes. If your heating needs power, ask the installer whether its pump may be connected to a station at all. Do not rely on a power station for medical equipment without the advice of your doctor or the equipment supplier.