Power station runtime: watt-hours, watts and the 85% rule of thumb
The formula
Runtime (hours) ≈ station capacity (Wh) × efficiency ÷ device draw (W).
We use 85% efficiency as a planning assumption. Real efficiency varies by load, temperature and unit; treat the result as an estimate.
Find the draw
The device's label or manual lists watts. If it lists amps and volts, watts = volts × amps. A fridge cycles on and off, so its average draw is lower than its label; we won't guess a number, so check its energy label.
Two limits, not one
- Capacity (Wh): how long.
- Output (W): how much at once. An appliance drawing more than the rated output will trip the station. The stations on our picks page list 1,800 W. For scale, Wikipedia's induction cooktop article notes early cooktops with ~1,600 W burners; a single such burner nearly maxes a 1,800 W station (Induction cooking).
Battery chemistry
LFP (lithium iron phosphate) cells are noted for better aging and cycle life, with cycle durability quoted in the thousands of cycles, and lower energy density than other lithium-ion types (Wikipedia). Anker states 3,000 cycles for its C1000 and BLUETTI 3,500+ for the AC180. Those are maker claims about how they define a cycle.
Recharging
Manufacturers list several ways: Anker says up to 600 W solar recharge on the C1000; BLUETTI lists AC, solar, car and generator input. Match the recharge method to your use: a car-camping user wants a 12 V input; a backup user wants fast AC.
What to avoid
- Buying by capacity alone; check output.
- Running heating appliances (space heaters, kettles) from a small station; they draw a lot.
- Assuming expandable capacity is included; it is usually a separate purchase.
- Indoor use without ventilation guidance from the manual.