Runtime calculator

Estimate how long a power station will run your device.

Enter battery watt-hours, device watts, inverter efficiency, and reserve. The result is a practical runtime estimate before comparing 300Wh, 500Wh, or 1000Wh power stations.

Estimated runtime 7.2 hours

A 500Wh class unit can cover this load for part of a day.

Inputs

Battery and load

Power station capacity Use the listed watt-hours, such as 300Wh, 500Wh, or 1000Wh. Device running watts Use measured watts if you have them. Labels can be rough. Inverter/load efficiency AC loads often waste more energy than DC or USB loads. Battery reserve Reserve helps avoid planning around every last watt-hour. Planned runtime target Used to estimate the battery size needed for your goal. Startup surge watts Use for fridges, pumps, compressors, and other motor loads.

Why runtime changes

Power station runtime depends on usable battery capacity, inverter losses, device cycling, temperature, battery age, and startup surge. Treat this as a planning estimate, then check the manual and real device wattage.

Runtime notes

What the runtime estimate is actually checking

The most useful number is not only battery capacity. A 500Wh power station does not always deliver 500Wh to an AC device, and a motor load may need more startup power than its average running watts suggest.

Watt-hours

Capacity is the fuel tank

Higher watt-hours usually means longer runtime, but reserve settings, inverter losses, and high loads reduce the usable amount.

Watts

Load size sets the burn rate

A 45W fan and a 90W TV can have very different runtime on the same battery. Measure the real load when possible.

Surge

Starting power can be the dealbreaker

Fridges, pumps, compressors, and tools can spike when they start. Check surge output before shopping by runtime alone.

Related checks

Match runtime, load size, and recharge time

Backup loads

Outage backup load planner

Build a complete load list when you need more than one device running.

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Recharge

Solar recharge time calculator

Check whether your solar panel can refill the battery in a usable window.

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Guide

300Wh vs 500Wh vs 1000Wh

Compare common size classes before choosing a power station.

Read guide