Power Station Runtime Calculator
Estimate how long a portable power station runs a given load, after inverter and battery-reserve losses.
Results
Estimated runtime: 7.2 h
Usable energy: 850 Wh
Phone charges: ≈ 57
12 V fridge runtime: ≈ 18.9 h
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 kg
- EcoFlow RIVER 2256 Wh · 300 W AC · 3.5 kg
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 power station run my device?
Multiply the station's watt-hours by about 0.85 for usable energy, then by 0.85 for AC (or 0.95 for DC), and divide by your device's watts. A 1000 Wh station runs a 100 W AC load about 7 hours.
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
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