How do I calculate power station runtime?

Multiply rated watt-hours by the usable-capacity percentage and conversion efficiency, then divide by the effective load in watts.

How long will a 1,000 Wh power station run a refrigerator?

Runtime depends on the refrigerator's measured running watts, compressor duty cycle, startup demand and conversion losses. Enter those values rather than relying on a universal average.

Can this calculator check startup surge?

No. Runtime is an energy calculation. Confirm continuous and surge output separately against the appliance and power-station manuals.

Power station runtime calculator

Calculate battery runtime

Use the rated battery capacity in watt-hours and the combined running watts of the equipment you plan to power. Adjust usable capacity, conversion efficiency and duty cycle instead of assuming every labelled watt-hour reaches the appliance.

Your battery and load

Rated battery capacity (Wh) Combined running load (W) Usable battery capacity (%) Conversion efficiency (%) Load duty cycle (%)Use 100% for a constant load. Use a measured duty cycle for equipment that switches on and off. Target runtime (hours)

Estimated runtime—

Energy delivered to load—After entered usable-capacity and efficiency assumptions

Rated capacity needed—For the entered target runtime

Effective average load—Running watts adjusted by duty cycle

Runtime estimate only. Confirm the power station's continuous and surge output, port limits, temperature range and appliance compatibility separately.

Runtime formula

Runtime hours = rated watt-hours × usable-capacity fraction × conversion efficiency ÷ effective load watts

Effective load is running watts multiplied by duty cycle. A steady 100 W device uses a 100% duty cycle. A compressor load may cycle, but the correct percentage should come from measurement or reliable equipment data.

How to get better inputs

Read rated capacity from the battery or power-station specification.
Measure appliance consumption with a plug-in meter where practical, or use the nameplate/manual.
Use 100% duty cycle unless the load is known to cycle.
Reduce usable capacity or efficiency to model conservative conditions.
Check startup surge separately for refrigerators, pumps, air conditioners and power tools.

Watts and watt-hours answer different questions. Watt-hours determine runtime. Continuous and surge watts determine whether the power station can start and supply the load at all.

Common runtime questions

How long will a power station run a refrigerator?

Use the refrigerator's measured running watts and compressor duty cycle. Then verify startup surge against the inverter specification. There is no reliable universal runtime from capacity alone.

How long will a battery run a CPAP?

Use the machine's actual wattage with your normal humidifier and heated-hose settings. Those features can materially change energy use.

Can I calculate microwave or air-fryer runtime?

Yes for energy, but first confirm the power station can supply the appliance's continuous input and startup demand. High-wattage cooking loads drain small batteries quickly.

Is inverter efficiency always 85%?

No. The default is an editable planning assumption, not a product claim. Replace it with manufacturer data or measured performance when available.

Need to size several appliances together?

Use the appliance-by-appliance worksheet to calculate daily energy, outage capacity and combined running output.

Open the home-backup sizing worksheet →

Comparing a larger portable system?

See how a published 3.6 kWh, 3,600 W unit fits selected-load backup, including the limits to check before buying.

Read the EcoFlow DELTA Pro guide →

Sources and method

Method reviewed 27 August 2026. SolarStateData does not collect or transmit calculator inputs.