Free online tool

Battery runtime calculator

Estimate real portable-power runtime from rated watt-hours after conversion loss, reserve, and duty cycle, not from the number on the box.

HS TOOL / 07

Estimate usable battery time.

Translate watt-hours into a bounded runtime scenario with efficiency, reserve, and duty cycle exposed.

COMMON WAYS TO ASK

How long will a power station run my fridge?
Calculate battery runtime
Watt-hours to hours

QUICK ANSWER

What this calculator tells you.

Convert rated watt-hours into realistic runtime by subtracting conversion loss and reserve, then dividing by the load and its duty cycle. The rating on the box is not the runtime you get.

WORKED EXAMPLE

A 1,000 Wh station running a 60 W load

INPUT85% efficiency · 20% reserve · 50% duty cycle

RESULTRuntime well beyond the naive 16 hours, because the load cycles

CHECK THE EDGE CASES

Questions people ask next.

Why is real runtime shorter than capacity divided by watts?

Inverters lose energy as heat, most systems hold a reserve rather than discharging to zero, and cold reduces usable capacity. Each of those is a separate input here rather than a hidden fudge factor.

What duty cycle should I use for a fridge?

A refrigerator runs its compressor intermittently, so its average draw is well below its rated watts. Measure with a plug meter if you can; otherwise treat the result as a range, not a promise.