Portable energy
Portable power station runtime calculations
Estimate realistic appliance runtime from watt hours, average load, startup power and conversion losses.
Published 2 September 2026 · General buying information
01
Use average watts, not only the appliance label
Some devices cycle on and off while others vary their power. A plug-in energy meter can provide a better average than a maximum label figure.
02
Apply an efficiency allowance
For a simple AC estimate, multiply rated watt hours by an allowance such as 0.8 to 0.9, then divide by average appliance watts. Treat the result as planning guidance, not a guarantee.
- Allow for inverter losses
- Account for cold or hot conditions
- Leave an emergency reserve
03
Check startup surge separately
Fridges, pumps and motor loads can briefly require much more power than their running consumption. The inverter must handle that startup even when total energy capacity is sufficient.
04
DC and USB loads can behave differently
Using a suitable DC or USB-C output can avoid some inverter loss. Check voltage, current and charging protocol compatibility before assuming it is more efficient.
05
Plan the recharge cycle
Runtime is only half of an off-grid plan. Compare the energy used each day with realistic solar, vehicle or mains energy available to replace it.
Common questions
Frequently asked questions
Will a 1,000 Wh station run a 1,000 W appliance for one hour?
Usually less than one hour because the full rated capacity is not delivered as usable AC energy and the load may vary.
Why does a fridge runtime estimate vary so much?
Ambient temperature, insulation, thermostat setting, door openings and compressor duty cycle all change average consumption.
Can solar input equal the panel rating all day?
No. Weather, angle, temperature, shading and charging limits reduce or vary real input.