Why is your power station running out faster than expected?

By the Ferncharge team · Figures last checked 21 October 2026

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The short answer: the watt-hours (Wh) on the box are not all available to your appliance. Some capacity is held back to protect the battery, the inverter loses some energy turning it into mains power, and the power station uses a little itself while it's on. Cold weather and an older battery take more off. BLUETTI's manual builds the first three into its own runtime formula (BLUETTI manual).

Based on manufacturers' published figures. Ferncharge has not tested these products. Estimates only.

Work out a runtime in the runtime calculator: it applies these losses and shows the working.

The maker's own formula

BLUETTI's Elite 100 V2 manual gives the operation time as:

capacity × depth of discharge × inverter efficiency ÷ (load + the power station's self-consumption)

It states a depth of discharge of 90%, inverter efficiency of over 90%, and self-consumption of about 10 W for that model (BLUETTI manual). Each part is one reason a power station runs out sooner than the label suggests.

1. Not all the capacity is usable

Batteries aren't run right down to empty. EcoFlow says lithium-ion and LiFePO4 batteries can have a depth of discharge of 70–90% (EcoFlow). BLUETTI's formula uses 90%. On a 1,000 Wh power station, that's about 900 Wh before any other loss.

2. The inverter loses energy

The mains (AC) sockets go through an inverter, which loses some energy. BLUETTI states over 90% efficiency; EcoFlow uses 0.90 as a planning assumption (EcoFlow). Together with the 90% depth of discharge, that leaves about 810 Wh of a 1,000 Wh battery at the mains socket: the figure our methodology uses.

Tip: if a device can run from the power station's USB or 12 V outputs instead of a mains plug, it skips the inverter.

3. The power station uses power itself

While it's switched on, a power station's screen, electronics and inverter draw a little power. BLUETTI puts the Elite 100 V2's at about 10 W (BLUETTI manual). Other models differ: check your manual.

This matters most with small loads. Using BLUETTI's formula and figures on a 1,000 Wh battery (our arithmetic):

Illustrative figures. Your power station's self-consumption and your appliance's real draw will differ.

Size a power station for a 10 W router: the sizing calculator adds a margin for standby use.

4. Cold weather

EcoFlow says that as temperatures fall a battery "can lose usable capacity" and runtime may drop, and that there's no universal percentage for every model (EcoFlow). For planning, its runtime guide uses an illustrative factor of 0.90 at 0 °C and 0.80 at -10 °C (EcoFlow).

Cold also affects charging. EcoFlow says the battery management system may slow or stop charging when the battery is too cold (EcoFlow), and BLUETTI states a charging range of 0 °C to 40 °C for the Elite 100 V2 (BLUETTI manual). A battery that didn't fully charge in a cold van or tent starts with less.

5. An older battery

Capacity falls as a battery ages. EcoFlow's runtime guide uses a 0.95 remaining-capacity factor, and says it's an illustrative planning assumption, not a warranty threshold (EcoFlow).

Putting it together (our arithmetic on EcoFlow's illustrative factors): 810 Wh × 0.90 (cold, at 0 °C) × 0.95 (age) is about 690 Wh available from a 1,000 Wh power station at the mains socket. In our runtime calculator, add a derate for cold or age to see the effect.

6. The appliance draws more than you think

• Typical figures are a guide. Use the watts on your appliance's rating label rather than a typical figure.
• Start-up and cycling: fridges and freezers switch their compressor on and off, and each start briefly draws more. See our freezer guide.
• Several things at once: add up everything plugged in, including chargers left connected.

7. It switched off, but isn't empty

Some power stations turn off an output by themselves when the load is small. BLUETTI says ECO mode is on by default on the Elite 100 V2 and shuts off the AC or DC output after a period of low or no load. It advises turning ECO mode off for small devices under 60 W and for appliances such as lights and fridges (BLUETTI manual). If a router or fridge stops while the battery still shows charge, check the ECO or auto-off setting in your manual.

FAQs

Why does my power station die faster than the Wh rating suggests?

Not all the rated capacity is usable, the inverter loses some energy, and the power station uses a little itself. On BLUETTI's figures, about 810 Wh of a 1,000 Wh battery reaches the mains socket, before self-consumption, cold or age.

Does a power station use power when nothing is plugged in?

Yes, while it's switched on. BLUETTI puts the Elite 100 V2's self-consumption at about 10 W. Turn the outputs or the unit off when you're not using them.

Do power stations run out faster in the cold?

They can. EcoFlow says usable capacity and runtime may drop as temperatures fall, with no single figure for every model, and that charging may slow or stop when the battery is too cold.

Why did my power station turn off with charge left?

It may be an ECO or auto-off mode. BLUETTI says its ECO mode shuts off an output after a period of low or no load, and advises turning it off for small devices and fridges.

Related: Runtime calculator · What size do I need? · How we work out runtimes · Power station safety