How many watts does a window AC use?

Cooling Also called: window ac, room air conditioner, window unit

Two numbers decide whether a power station runs a window air conditioner, and readers arrive using them interchangeably. Watts are the ceiling on what the inverter can hold at any instant — this load needs 833 W of them while it runs, and 6,900 W for the moment it starts. Watt-hours are how much energy the battery holds. A machine can have plenty of one and not enough of the other.

Of the 26 station records we publish — every model we hold a page for, with its US and EU versions counted separately — 2 run it, 0 are a tight fit and 24 are out of reach. Each of those is a calculation against that machine’s continuous output, its surge ceiling and its inverter waveform — not a lookup table — and the reasoning is on every row.

The three numbers a power station is judged against

Running power 833 W 667–1,000 W Derived from official coefficients · verified 2026-08-03 · medium confidence

Start-up surge 6,900 W engine checks 6,900 W Derived from official coefficients · verified 2026-08-01 · medium confidence

Duty cycle 90% Official spec · verified 2026-08-03 · medium confidence

The band is the spread across real models in this class, not a tolerance. Size against the top of it unless you know which unit you own.

Start-up figure: Manufacturer nameplate (locked-rotor)

This record publishes both an absolute inrush and a multiple of running power. They do not agree exactly, so the engine checks against the more demanding of the two — 6,900 W — rather than picking the flattering one.

Measured duration 200 ms · Official spec · verified 2026-08-03 · low confidence

Two ways to read a duty cycle

A duty cycle can be read two ways and they are not the same number. One is the constant a test procedure assumes so that a label figure is reproducible; the other is what the machine does in a real room, which depends on the weather, the door and the thermostat. The named readings below each carry their own source and date, so you can see which one a figure came from rather than being handed a blend of the two.

Outdoor 83°F (28.3°C) 12% Official spec · verified 2026-08-01 · medium confidence
Outdoor 95°F (35°C) default 18% Official spec · verified 2026-08-01 · medium confidence
Commercial setting, outdoor 95°F 90% Official spec · verified 2026-08-01 · medium confidence
DOE annual average (750 cooling hours/year) 8.6% Derived from official coefficients · verified 2026-08-03 · medium confidence

Official spec + Derived from official coefficientsverified 2026-08-03appliance record

What actually decides it

A motor load: the first half-second decides it

An induction motor with a stationary rotor is close to a short circuit. For the fraction of a second before it turns, it pulls several times its running current, and that peak — not the running figure — is what trips an inverter. This is why a machine drawing well under a station’s continuous rating can still fail to start on it, and why the start-up figure at the top of this page matters more than the running one.

What kind of motor is inside

It is a rotary compressor. The inrush is shorter than a piston machine’s but the running draw is higher, so both ends of the check matter here.

How long the start-up actually lasts

The inrush lasts a couple of tenths of a second, which is the window a station’s surge rating is written for. This is the one case where the surge figure and the surge ceiling are directly comparable.

Watts are not what the inverter is holding

At a power factor of 0.90 this load presents 926 VA to the inverter. An inverter is sold in watts and limited in volt-amps, so a machine that looks comfortable on the watt figure can be at its ceiling on the VA one. The engine checks both.

Which power stations run it

Every row is a live calculation against that machine's continuous output, surge ceiling and inverter waveform. Of the 26 station records we publish — US and EU versions counted separately — 2 run it, 0 are a tight fit and 24 are out of reach. The percentage is this load as a share of that machine's continuous output; anything past 82% drops out of the green. Rows are ordered by verdict, then by price — cheapest first inside each band.

EcoFlow DELTA Pro 3 EcoFlow · US 120 V 4,000 W continuous · 8,000 W surge ceiling Runs it21%

750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: 4 of EcoFlow’s own published documents, read 2026-08-08, carry no depth of discharge or inverter efficiency for the US 120 V build, so there is no defensible usable-capacity figure to divide. $2,799 · checked 2026-08-17 Show the working →

EcoFlow DELTA Pro 3 EcoFlow · EU 230 V 4,000 W continuous · 8,000 W surge ceiling Runs it21%

750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: we have found no depth of discharge or inverter efficiency for the EU 230 V build, so there is no defensible usable-capacity figure to divide. €3,299 · checked 2026-08-17 Show the working →

BLUETTI Elite 30 V2 BLUETTI · US 120 V 600 W continuous Too big139%

limited by continuous output We have found no published surge rating for the US 120 V build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. $239 · checked 2026-08-17 Show the working →

EcoFlow RIVER 3 Plus EcoFlow · US 120 V 600 W continuous · 1,200 W surge ceiling Too big139%

limited by continuous output 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: 4 of EcoFlow’s own published documents, read 2026-08-08, carry no depth of discharge or inverter efficiency for the US 120 V build, so there is no defensible usable-capacity figure to divide. $279 · checked 2026-08-17 Show the working →

Jackery Explorer 300 Plus Jackery · US 120 V 300 W continuous · 600 W surge ceiling Too big278%

limited by continuous output $299.99 · checked 2026-08-17 Show the working →

BLUETTI Elite 100 V2 BLUETTI · US 120 V 1,800 W continuous · 3,600 W surge ceiling Too big192% of surge ceiling

limited by surge ceiling $499 · checked 2026-08-17 Show the working →

Jackery Explorer 1000 v2 Jackery · US 120 V 1,500 W continuous · 3,000 W surge ceiling Too big230% of surge ceiling

limited by surge ceiling $549 · checked 2026-08-17 Show the working →

EcoFlow DELTA 3 Plus EcoFlow · US 120 V 1,800 W continuous · 3,600 W surge ceiling Too big192% of surge ceiling

limited by surge ceiling 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: 3 of EcoFlow’s own published documents, read 2026-08-08, carry no depth of discharge or inverter efficiency for the US 120 V build, so there is no defensible usable-capacity figure to divide. $719 · checked 2026-08-17 Show the working →

BLUETTI Elite 200 V2 BLUETTI · US 120 V 2,600 W continuous Too big265% of assumed surge ceiling

limited by surge ceiling We have found no published surge rating for the US 120 V build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. $899 · checked 2026-08-17 Show the working →

Jackery Explorer 2000 Plus Jackery · US 120 V 3,000 W continuous · 6,000 W surge ceiling Too big115% of surge ceiling

limited by surge ceiling $899 · checked 2026-08-17 Show the working →

Jackery Explorer 1000 Plus Jackery · US 120 V 2,000 W continuous · 4,000 W surge ceiling Too big173% of surge ceiling

limited by surge ceiling $999 · checked 2026-08-17 Show the working →

EcoFlow DELTA 2 Max EcoFlow · US 120 V 2,400 W continuous · 4,800 W surge ceiling Too big144% of surge ceiling

limited by surge ceiling 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: 5 of EcoFlow’s own published documents, read 2026-08-08, carry no depth of discharge or inverter efficiency for the US 120 V build, so there is no defensible usable-capacity figure to divide. $1,049 · checked 2026-08-17 Show the working →

EcoFlow STREAM Ultra EcoFlow · US 120 V 800 W continuous Too big104%

limited by continuous output 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: 3 of EcoFlow’s own published documents, read 2026-08-08, carry no depth of discharge or inverter efficiency for the US 120 V build, so there is no defensible usable-capacity figure to divide. We have found no published surge rating for the US 120 V build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. $1,279 · checked 2026-08-17 Show the working →

BLUETTI Elite 30 V2 BLUETTI · EU 230 V 600 W continuous Too big139%

limited by continuous output We have found no published surge rating for the EU 230 V build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. €219 · checked 2026-08-17 Show the working →

Anker SOLIX C300 Anker SOLIX · EU 230 V 300 W continuous · 600 W surge ceiling Too big278%

limited by continuous output 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: we have found no depth of discharge or inverter efficiency for the EU 230 V build, so there is no defensible usable-capacity figure to divide. €269.99 · checked 2026-08-01 · 17 days ago Show the working →

Jackery Explorer 300 Plus Jackery · EU 230 V 300 W continuous · 600 W surge ceiling Too big278%

limited by continuous output 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: we have found no depth of discharge or inverter efficiency for the EU 230 V build, so there is no defensible usable-capacity figure to divide. €279 · checked 2026-08-17 Show the working →

EcoFlow RIVER 3 Plus EcoFlow · EU 230 V 600 W continuous · 1,200 W surge ceiling Too big139%

limited by continuous output 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: we have found no depth of discharge or inverter efficiency for the EU 230 V build, so there is no defensible usable-capacity figure to divide. €299 · checked 2026-08-01 · 17 days ago Show the working →

Jackery Explorer 1000 v2 Jackery · EU 230 V 1,500 W continuous · 3,000 W surge ceiling Too big230% of surge ceiling

BLUETTI Elite 100 V2 BLUETTI · EU 230 V 1,800 W continuous Too big383% of assumed surge ceiling

limited by surge ceiling We have found no published surge rating for the EU 230 V build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. €579 · checked 2026-08-17 Show the working →

EcoFlow STREAM Ultra EcoFlow · EU 1,200 W continuous Too big575% of assumed surge ceiling

limited by surge ceiling 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: we have found no depth of discharge or inverter efficiency for the EU build, so there is no defensible usable-capacity figure to divide. We have found no published surge rating for the EU build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. €599 · checked 2026-08-17 Show the working →

EcoFlow DELTA 3 Plus EcoFlow · EU 230 V 1,800 W continuous · 3,600 W surge ceiling Too big192% of surge ceiling

EcoFlow DELTA 2 Max EcoFlow · EU 230 V 2,400 W continuous · 4,800 W surge ceiling Too big144% of surge ceiling

Anker SOLIX Solarbank 3 E2700 Pro Anker SOLIX · EU 1,200 W continuous Too big575% of assumed surge ceiling

limited by surge ceiling 750 Wh per hour — averaged over this load’s duty cycle — assumes near-continuous outage duty (90%), a scenario assumption — not a typical-use average or a manufacturer figure No runtime in hours: we have found no depth of discharge or inverter efficiency for the EU build, so there is no defensible usable-capacity figure to divide. We have found no published surge rating for the EU build. The start-up check runs against its continuous output as a conservative floor, which is ours, not a manufacturer specification. €999 · checked 2026-08-01 · 17 days ago Show the working →

Jackery Explorer 1000 Plus Jackery · EU 230 V 2,000 W continuous · 4,000 W surge ceiling Too big173% of surge ceiling

BLUETTI Elite 200 V2 BLUETTI · EU 230 V 2,600 W continuous Too big265% of assumed surge ceiling

Jackery Explorer 2000 Plus Jackery · EU 230 V 3,000 W continuous · 6,000 W surge ceiling Too big115% of surge ceiling

Which one to buy, ranked

Our pick for this load

EcoFlow DELTA Pro 3 · US 120 V

The cheapest US 120 V machine in the list that runs a window air conditioner outright, and it holds it at 750 Wh per hour.

$2,799 · price checked 2026-08-17

The buy link is in the bar at the bottom of the screen — one action per page, and it goes to the merchant we last checked the price at.

What changes the numbers

At 28.3 °C ambient ×0.7 Applied to how OFTEN it runs, not to how hard it pulls while running. The verdict does not move; the energy it costs you over a day does. Official spec

At 35 °C ambient ×1 Applied to how OFTEN it runs, not to how hard it pulls while running. The verdict does not move; the energy it costs you over a day does. Official spec

Between the anchors Only the anchor points above have a source. This site does not interpolate between them: a curve drawn through two published points is a number we invented, and it would arrive on the page wearing the same official label as the points it was drawn from.

Mains standards on record US 120 V · EU 230 V The figures above are recorded per mains standard, because the same appliance class is built differently on 120 V and 230 V. Where only one standard is on record, the ranking still lists machines from both regions — each row states its own.

Everything else we hold on this load

Each figure carries the tier it came from and the date it was checked. Sizing guidance is kept apart from measured draw on purpose: one says what the machine pulls, the other says what a manufacturer or a standard thinks you should buy for it.

Measured and published draw

Power factor 0.90 Derived from official coefficients · verified 2026-08-03 · medium confidence

The inverter is loaded to 926 VA — 833 W ÷ 0.90 — which is the figure its ceiling is actually measured against.

Energy per year 625 kWh Derived from official coefficients · verified 2026-08-03 · medium confidence

Not a published figure: computed from this load’s running draw and its duty cycle, which is why its confidence sits below the specs around it.

Cycle period 3 min Official spec · verified 2026-08-01 · high confidence

Sizing guidance — not a draw figure

Minimum continuous output 1,118 W Official spec · verified 2026-08-01 · medium confidence

A sizing figure, not a draw: it is what this class needs a machine to be RATED at, headroom included.

Where to go next

From the Knowledge channel

A window air conditioner has a dedicated guide: the same records this page computes from, worked through in prose with room for the reasoning a table can only summarise — Does a U-shaped inverter window AC make a power station’s job easier?

Questions people ask about this load

How many watts does a window air conditioner use?

833 W while it is running, and 667–1,000 W across the models in this class, with 6,900 W demanded at the instant it starts. Those are different questions and most pages answer only the first. The running figure decides whether a machine can hold it; the start-up figure decides whether it can get it going at all, and it is usually the one that fails. The start-up figure here is the manufacturer’s own..

What size power station do I need for a window air conditioner?

For a window air conditioner, the EcoFlow DELTA Pro 3 (US 120 V) is the cheapest machine in our library that runs it, at 4,000 W continuous · 8,000 W surge ceiling and $2,799 against a running draw of 833 W and a start-up demand of 6,900 W. That is a verdict computed from this load’s running watts, its start-up demand and the inverter waveform — not a rule of thumb about doubling the wattage. 2 of 26 machines clear it.

How long will a power station run a window air conditioner?

We do not print one here, and the reason is in the rows rather than in our data. 10 of the 26 machines above hold everything the division needs — and every one of them is a machine that will not start a window air conditioner, where an hour figure would be describing an hour that never happens. None of the machines that do run it prints one either: each of those rows names the published figure we could not find, rather than dividing a nameplate watt-hour rating by a label wattage, which runs typically 20–35% high.

Why does a window air conditioner need so much more power to start?

The start-up figure is the manufacturer’s own locked-rotor rating, off a spec sheet for a real model in this class — not a category multiple. Where a standards table and the nameplate disagree, this library uses the nameplate: the standards figure is a selection envelope for breakers and controllers, and sizing a battery to it over-specifies the machine by two to four times. The engine works the check against 6,900 W, which is what a station's surge ceiling has to cover for the moment the machine starts. A station whose continuous rating is comfortably above the running figure can still refuse the start, and that is the single most common way a purchase goes wrong for this class.

Does a window air conditioner draw that continuously?

No, and the difference is most of the energy question. This record holds more than one duty-cycle reading, each with its own source: Outdoor 83°F (28.3°C) at 12%, Outdoor 95°F (35°C) at 18%, Commercial setting, outdoor 95°F at 90%, DOE annual average (750 cooling hours/year) at 8.6%. The one a page picks silently is the one that decides whether your battery lasts the night, so this site names them and lets you choose in the calculator rather than blending them into a single average.