Power Station Runtime Calculator: How Long Will It Run?

Power station boxes advertise watt-hours, but nobody plugs in a watt-hour. What you actually want to know is how long will this run my fridge, my CPAP, or my sump pump? That's a division problem, with one correction for the energy the inverter burns as heat. Enter your loads and pick a station.

The Calculator

Estimates only. Real runtime moves with temperature, battery age, and how hard the load actually works; check the station maker's own figures for your exact model.

How the Math Works

Jackery publishes the formula it uses for its own runtime estimates: working time = capacity (Wh) x 0.85 / the device's operating wattage. The 0.85 covers the energy lost turning stored battery power into usable outlet power. Jackery's worked example is a 2,042.8Wh station running a 400W device for about 4.3 hours.

Two rules sit on top of that formula:

• Output caps what you can run, capacity caps for how long. A big battery can't start a load bigger than its inverter's continuous output rating. That's why the calculator checks your total against the station's watt rating before it reports hours.
• Loads add together. Two 100W devices draw like one 200W device, so runtime halves.

Finding Your Device's Watts

Look for the label or nameplate on the device or its power brick. If it lists watts (W), use that. If it lists volts and amps instead, multiply them: a 120V device drawing 1.5A uses about 180W. Devices with motors or compressors, like refrigerators and freezers, cycle on and off. Running the calculator on their full running wattage gives you a conservative, worst-case number.

Quick Reference: Hours Per 1,000Wh

Scale by your station's size: a 2,000Wh station doubles each figure, a 500Wh station halves it.

Common Questions

Why not just divide capacity by watts?

Because some stored energy is lost as heat converting battery power into usable outlet power. Jackery's formula applies a 0.85 factor for that, so dividing raw Wh by watts overstates runtime.

Can I add solar or recharge while running?

Many stations support pass-through charging and solar input, which stretches runtime past this estimate. Check your model's specs for its input limits. The power station guide covers which models take solar.

Battery or gas generator for outages?

If your total load is small and you want silent, indoor-safe power, a battery fits. For long outages, well pumps, or heavy loads, a fuel generator wins on hours. See battery backup vs. gas generator for the full comparison.

Bottom Line

Runtime is a division problem: capacity x 0.85 / watts. Size the station so its output covers everything you'll run at once, then buy enough watt-hours for the hours you need.