Power It Up: running a window air conditioner on battery
Work out a window AC's watts from its BTU and efficiency rating, then see how long a power station lasts.
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Watts ≈ BTU per hour ÷ efficiency rating (EER or CEER). A 5,000 BTU unit rated 11 runs about 455 W while the compressor is on. A 1kWh-class station gives under 2 hours of continuous cooling at that figure; overnight cooling needs several kWh.
- Watts ≈ BTU ÷ EER (or CEER).
- Compressor start-up surge needs a high surge rating.
- Cooling one small room only when needed stretches runtime.
What a window air conditioner draws
| Item | Example figure | Where it comes from |
|---|---|---|
| Cooling size (example) | 5,000 BTU/h | On the unit's label |
| Efficiency (example) | CEER 11 | On the label or spec sheet |
| Running watts | ≈455 W | 5,000 ÷ 11 |
| 8 hours with the compressor always on | ≈3,640 Wh | 455 × 8 (worst case; real compressors cycle) |
How we do the math
Runtime (hours) ≈ usable watt-hours ÷ the device's average watts. Our reference set is five portable power stations whose specs we compiled in the Spec Check series. Estimated usable AC energy (our estimate: usable ≈ rated Wh × 0.80 (usable depth, Victron LiFePO4 data) × 0.92 (inverter, the NREL PVWatts manual derate) ≈ 0.736. Applying these to a power station gives a planning estimate, not a measurement): RIVER 3 ≈180Wh, DELTA 3 ≈754Wh, Anker C1000 ≈777Wh, Jackery 1000 v2 ≈788Wh, BLUETTI AC180 ≈848Wh.
Every device wattage on this page is an example. Read your own device's label or EnergyGuide sticker, or measure it with a plug-in energy meter, then put your number into the Power Planner.
Runtime on each reference station
| Power station | Est. usable Wh | Est. runtime |
|---|---|---|
| EcoFlow RIVER 3 | ≈180 | Not suitable (300W outlet) |
| EcoFlow DELTA 3 | ≈754 | ≈1.7 h |
| Anker SOLIX C1000 | ≈777 | ≈1.7 h |
| Jackery Explorer 1000 v2 | ≈788 | ≈1.7 h |
| BLUETTI AC180 | ≈848 | ≈1.9 h |
The smallest station that fits
For the compressor start, the stations with the biggest surge ratings are the DELTA 3 (3,600W) and the Jackery 1000 v2 (3,000W). BLUETTI's FAQ says not to use its Power Lifting Mode for an air conditioner, so plan on the AC180's standard 1,800W rating. For a full night, plan on an expandable unit such as the DELTA 3 with extra batteries, plus solar or a generator to refill.
EcoFlow DELTA 3 (1,024Wh)
3,600W surge for compressor starts; expandable up to 5kWh.
Check price on Amazon (opens in a new tab)FAQ
How do I find my AC's watts?
Look for a watts or amps figure on the label. If you only have amps, watts ≈ amps × 120 V. Or use BTU ÷ EER. A plug-in meter gives the real running number.
Where do I go next?
Try the power planner to put numbers to your own situation, or see the product picks on the deals page.
Terms used here
- Watt (W)
- Rate of power use or production.
- Watt-hour (Wh)
- Energy: one watt for one hour.
- Kilowatt-hour (kWh)
- 1,000 watt-hours.
- Depth of discharge (DoD)
- Share of a battery's capacity that is used.
- LiFePO4 (LFP)
- Lithium iron phosphate battery chemistry.
- Inverter
- Converts DC battery power to AC household power.
- Surge rating
- Short-term peak power an inverter can supply.
- Derate
- Factor for real-world losses in solar output.
Sources
This guide is informational and based on published specifications and general references, not hands-on testing. Check the manufacturer's current specs before you buy.