Portable Power Station Runtime Calculator

Estimate how long a portable power station or battery backup can run an appliance after accounting for capacity, efficiency, reserve power, standby draw, and appliance duty cycle.

Power Station

Battery Capacity (watt-hours)

Output Efficiency (%)

Battery Reserve (%)

Power Station Standby Draw (watts)

Output efficiency accounts for conversion losses. AC-powered equipment normally has greater losses than equipment connected directly to a compatible DC or USB output.

Appliance or Device

Common Appliance Preset

Device Running Watts

Number of Identical Devices

Estimated Duty Cycle (%)

Planned Use Per Day (hours)

Duty cycle is the percentage of operating time during which the appliance actively draws its running wattage. Devices such as refrigerators, freezers, and sump pumps normally cycle on and off.

Power Station Runtime Estimate

Active Connected Load —

Estimated Average Draw —

Usable Battery Energy —

Estimated Operating Runtime —

Estimated Daily Energy Use —

Estimated Days at Planned Use —

Battery Capacity Needed for 24 Hours —

This estimate is based on average energy use. Motor starting surge, battery temperature, battery age, inverter limits, power-station shutdown settings, and the actual appliance cycle can change real-world runtime.

How Long Will a Portable Power Station Run an Appliance?

Runtime depends on the power station’s watt-hour capacity and the appliance’s average wattage. A 1,000-watt-hour battery does not normally provide the full 1,000 watt-hours to connected equipment because some energy is lost during conversion and some may be held in reserve.

Runtime = usable watt-hours ÷ average watts

Watt-Hours Versus Watts

Watts measure how quickly a device uses power. Watt-hours measure stored energy. A device drawing 100 watts for five hours uses approximately 500 watt-hours of energy.

Watt-hours used = watts × hours

What Is Power Station Efficiency?

A power station uses energy to operate its inverter, electronics, cooling fans, and display. Converting battery power to household AC power also creates losses. An 85% efficiency estimate is a reasonable planning starting point, but actual efficiency varies by model, output type, load, and operating conditions.

What Is Appliance Duty Cycle?

Some devices draw power continuously, while others cycle on and off. A refrigerator may draw 150 watts while its compressor runs but operate for only part of each hour. A 35% duty-cycle estimate treats that refrigerator as an average load of approximately 52.5 watts before accounting for additional standby power.

Average device watts = running watts × duty-cycle percentage

Can a Power Station Run a Refrigerator or Freezer?

The battery may contain enough energy for the estimated runtime while still being unable to start the compressor. Confirm that the power station’s continuous-output and surge-output ratings exceed the appliance’s running and startup requirements.

Can a Power Station Run a CPAP Machine?

CPAP power use varies considerably with pressure, heated tubing, humidification, mask leakage, and whether the machine uses AC or direct DC power. Use the device’s actual power information whenever possible and test the complete setup before depending on it overnight.

Portable Power Station Safety

Follow the power-station and appliance manufacturers’ instructions. Keep the unit dry, provide required ventilation, use properly rated cords, and do not exceed continuous or surge-output limits. Battery power stations do not produce combustion exhaust, but connected appliances may have their own ventilation and safety requirements.