Why a Power Station Won't Run Your Space Heater, AC, or Well Pump
Why a power station rated for 2000 watts still cannot run a space heater, window AC, or well pump, and how surge and continuous loads differ.
You bought a power station rated for 2000 watts, plugged in a 1500-watt space heater, and it shut off, or drained in minutes. Or it runs your fridge fine until the compressor kicks on, then trips. That’s one of the most common power-station complaints, and it almost always comes down to something the spec sheet glosses over. A station can fail for two completely different reasons, and they have nothing to do with each other.
We didn’t test these appliances. The wattage and surge figures below are the typical ranges that manufacturers and electrical references report, and they vary by model.
Two failure modes, not one
- Resistive loads (anything that makes heat) draw their full wattage continuously, with little or no startup spike. Space heaters, electric kettles, hair dryers, and toasters. There’s no surge to blame here. It’s sustained high draw that both crowds the station’s watt rating and empties the battery quickly.
- Inductive loads (anything with a motor) pull a brief but large surge at startup to overcome inertia, then settle to a much lower running draw. Refrigerators, air conditioners, well pumps, and power tools all behave this way. The trouble is that momentary spike.
Keep the two apart in your head. The fix is different for each.
Why a 1500-watt heater is the worst case
Resistive heat is brutal on a battery precisely because it’s honest. It pulls its rated power the entire time. In North America, portable space heaters cap near 1500 watts, roughly the safe continuous ceiling of a standard 15-amp, 120-volt circuit, a limit owners discuss constantly in electrical forums. There’s no clever surge to engineer around. It just draws 1500 watts until you turn it off.
That sustained draw does two things at once. It eats into the station’s continuous-watt rating, and it drains capacity fast. OUPES puts numbers on it: even a large battery empties quickly at 1500 watts, with a roughly 3000 Wh unit giving only about two hours and a 1200 Wh unit around 40 minutes. On a 1000-watt-rated station, a 1500-watt heater won’t run at all. Heating off a battery is expensive and short, which is why owners get steered toward fuel, or toward not heating large spaces on stored power in the first place.
Why motors trip a station that looks big enough
Motors are the other story. To get spinning, a motor briefly pulls far more than its running watts, commonly cited at 2 to 3 times and up to about 7 times for hard-starting motors, all in a fraction of a second. Motor nameplates often list this as Locked Rotor Amps (LRA), the inrush current at the instant of startup. As BLUETTI explains, starting watts are roughly volts times LRA, and that’s why a pump’s momentary draw can run several times its running figure.
| Appliance | Running watts | Starting (surge) watts |
|---|---|---|
| Refrigerator | ~200–700 W | ~1200–2200 W |
| Sump / well pump | ~800 W | ~2000 W |
| Central air conditioner | ~3500 W | ~6000 W |
| Space heater (resistive) | ~1500 W | ~1500 W (no surge) |
Why “1000 W running / 2000 W surge” still fails
Here’s the trap. A station advertised as, say, “1000 W running, 2000 W surge” can still refuse a well pump or an AC unit, and for either of two reasons. If the motor’s inrush exceeds the surge rating, the station’s overload protection trips before the motor spins up, and the appliance never starts. If the motor’s running watts exceed the continuous rating, it might start and then drop out a second later. The surge rating is brief and limited. It’s not a license to run any motor of that size.
So the practical rule has two halves. Match the continuous-watt rating to the load’s running watts, and make sure the surge rating clears the load’s startup surge. Resistive loads stress the energy budget. Motor loads stress the surge budget.
A quick word on waveform
There’s one more thing that trips people up, mostly with cheaper inverters: modified sine wave versus pure sine wave output. Modified sine is a rougher approximation of grid power. As Samlex America notes, it can run AC motors hotter and less efficiently, and it can upset microwaves, devices with timers or digital clocks, variable-speed controls, and sensitive electronics. Most modern battery power stations already output pure sine, so this mainly matters with budget inverters. For any medical device, don’t guess. Confirm the required waveform with the device manufacturer.
Where the sources genuinely disagree
The startup multiplier is a range, not a constant. Sources cite 2 to 3 times as typical and up to 7 times for hard-starting motors, and the real figure depends on the motor, the load, and whether a soft starter is fitted. Whether a given station starts a given fridge is genuinely device-specific. Frame it as “depends on this motor’s inrush versus the station’s surge spec,” and don’t treat any single number as a guarantee either way.
Bottom line
A power station shuts off for one of two reasons: a resistive load too big to sustain, or a motor surge too big to start. Size for both. Continuous watts for the running load, surge watts for the startup spike, and watt-hours for how long it has to last. To get the underlying units straight, read Watts vs Watt-Hours: Why Most People Size a Power Station Wrong, and to choose the right backup category in the first place, see the backup power decision framework.
Wattage and surge figures are typical ranges from the cited sources and vary by model. Always check the label on your specific appliance.