rewlogan/power
Portable power station calculator
How long is the outage?
You can shorten each device’s runtime below
Which devices need power?
Pick from the catalogue or start with a preset
Selected devices
No devices selected
Select at least one device to calculate your requirements.
Find a power station
Matched power stations
Choose devices first
Then we'll match power stations by capacity and output.
This tool provides estimates. Always verify the result against the specifications of your devices and power station.
How to calculate the power station capacity you need
1Add up your devices’ energy use
Multiply each device’s power in watts by its runtime in hours, then add the results to get watt-hours. If the outage lasts 8 hours but you only need your laptop for 3, count 3 hours for the laptop.
2Allow for losses and a reserve
Not all the energy printed on the battery label reaches your devices. Power conversion and the station itself use some energy. The calculator accounts for these losses and adds a reserve. You can inspect the assumptions in the calculation breakdown.
3Check output separately
The station’s continuous output must cover everything you run at once. Its surge rating must also handle short spikes from motors or compressors. A large battery does not compensate for insufficient power output.
Example: a router and a laptop
A 12 W router uses 96 Wh in 8 hours, and a 60 W laptop uses 180 Wh in 3 hours. That is 276 Wh before losses and reserve. If both run together, they draw 72 W.
Frequently asked questions
What is the difference between watts and watt-hours?
Watts (W) measure how much power a device draws at a given moment. Watt-hours (Wh) measure the energy it uses over time. Output tells you whether a station can run your devices; capacity helps estimate how long it can run them.
How do I estimate the runtime of a station I already own?
Add your devices and set their runtimes, then choose “I own a station” in the station section. Pick your model or enter its specifications manually. The estimate depends on your devices, the battery charge and condition, and conversion losses.
What size power station do I need for a refrigerator?
Check both daily energy consumption and the compressor’s startup power. A refrigerator cycles on and off, and startup can briefly increase its load. Select the refrigerator type in the calculator. Use a plug-in meter or the manufacturer’s figures when available.
Why might real runtime differ from the estimate?
The calculator provides an estimate. Device power draw can change, and temperature, battery charge, battery condition and the type of connection all affect usable energy. Verify the result against the specifications of your devices and power station.
How much extra battery capacity should I allow for?
The calculator starts with a 5% reserve. Increase it in the calculation breakdown if the load is uncertain or the outage could run longer. A capacity reserve does not replace checking the station’s surge rating.
Can a power station run a kettle or microwave?
Compare the appliance’s input power with the station’s continuous AC output. For a microwave, use the input rating on the label, not the cooking output. If you run two high-power appliances together, add their loads.
What if none of the listed stations can handle my setup?
Try shortening runtimes or leaving out non-essential devices. If battery capacity is the limit, consider a compatible expansion battery. For extended backup, you may need a stationary inverter with batteries or a generator.