Power Station Runtime Calculator

Estimate how long a portable power station runs a given load, after inverter and battery-reserve losses.

The formula, every assumption, and the primary sources behind this tool are published on this page.

Power station model

Battery capacityTotal battery capacity in watt-hours (Wh)

LoadTotal power draw of your devices

Load type

ACDC

AC uses the inverter (~85% efficiency); DC uses USB / 12 V ports (~95%).

Reset

Results

Example — computed from the default inputs above. Change any field and press Compute.

Estimated runtime: 7.2 h

Usable energy: 850 Wh

Phone charges: ≈ 57

12 V cooler before conversion losses: ≈ 18.9 h

1,000 × 0.85 × 0.85 ÷ 100 = 7.225 hUsable fraction 85% | AC efficiency 85%

Power stations that fit your result

These models meet the capacity and continuous output you calculated, from smallest capable to larger.

EcoFlow RIVER 3245 Wh · 300 W AC · 3.5 kg
Jackery Explorer 240 v2256 Wh · 300 W AC · 3.6 kgView manufacturer specs
EcoFlow RIVER 2256 Wh · 300 W AC · 3.5 kg

How long will a 500, 1,000, or 2,000 Wh power station last?

Estimated hours with 85% usable capacity and 85% AC or 95% DC efficiency. Loads are examples; the cooler uses a cycle-averaged estimate. Check your device's actual draw, output limits, and startup power.
Device / load	500 Wh	1,000 Wh	2,000 Wh
Laptop50 W AC	7.2 h	14.5 h	28.9 h
Electric blanket100 W AC	3.6 h	7.2 h	14.5 h
12 V cooler45 W DC	9 h	17.9 h	35.9 h

Select a result to load its inputs into the calculator.

Plan your setup: Find the power station size you need · Estimate solar charging time.

How it works

Only part of a station's rated watt-hours reach your device: the BMS keeps a reserve and the inverter (or DC path) loses some to conversion.

runtime_h = capacity_wh × 0.85 × efficiency / load_w

capacity_wh: Rated battery capacity, from the catalog model or your entry, in watt-hours.
usable_wh: Energy above the BMS reserve — capacity × 0.85.
efficiency: Conversion efficiency: 0.85 for AC (inverter) or 0.95 for DC ports.
load_w: Continuous power your device draws, in watts.
runtime_h: Estimated hours until the station shuts off.

Assumptions

Usable energy is 85% of the nameplate rating; the BMS cuts off before 0% to protect the cells.
AC loads pass through the inverter at ~85% efficiency; DC-port loads keep ~95%. Real efficiency varies with load level.
Phone charges assume a 15 Wh phone battery; fridge runtime assumes a 45 W (cycle-averaged) 12 V cooler. Both ignore conversion losses and are rough guides.
The load is treated as constant. Devices that cycle (fridges, tools) run longer than a constant-draw estimate.

FAQ

How long will a 1,000 Wh power station run a 100 W device?

About 7.2 hours on AC: 1,000 Wh × 0.85 usable capacity × 0.85 inverter efficiency ÷ 100 W. At the same 100 W through a DC port, the 95% conversion assumption gives about 8.1 hours. Actual runtime depends on the device's draw and the station's efficiency.

Why is runtime less than capacity ÷ watts?

The rated watt-hours are the cell total. The BMS keeps a reserve and the inverter loses energy to heat, so a 1000 Wh unit delivers roughly 720 Wh to an AC load.

Does AC or DC last longer?

DC (USB, 12 V) skips the inverter, so it wastes less — about 10% more runtime than the same wattage on AC.

Sources

Virginia Cooperative Extension — Estimating Appliance and Home Electronic Energy Use

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