What size generator for window air conditioner?
Check, uncheck or adjust the typical device list below — watts, startup surge and battery size update instantly. Numbers come from U.S. DOE, ENERGY STAR and manufacturer spec sheets, not marketing copy.
1. Check what you need to power
Refrigeration & Freezers
Kitchen
Heating, Cooling & Fans
- 1
Water & Pumps
Laundry & Cleaning
Electronics & Office
- 1
- 2
Medical Devices
Power Tools & Outdoor
Lighting
2. Your sizing
Assumptions: daily hours per device follow DOE / ENERGY STAR duty cycles; capacity adds a 25% margin. Check your appliance nameplates — actual draw varies by model.
3. Best matches from our 6-brand database
- EcoFlow DELTA 3 Max Plusexpandable system~$1,149
- rated 3,000W covers your 920W continuous load
- surge 6,000W covers your 2,435W start peak
- base 2,048Wh + expansion batteries (up to 10,000Wh) covers your 8,600Wh need
- EcoFlow DELTA Pro 3expandable system~$2,799
- rated 4,000W covers your 920W continuous load
- surge 8,000W covers your 2,435W start peak
- base 4,096Wh + expansion batteries (up to 12,288Wh) covers your 8,600Wh need
- 120/240V split-phase output
- Jackery Explorer 2000 Plusexpandable system~$2,599
- rated 3,000W covers your 920W continuous load
- surge 6,000W covers your 2,435W start peak
- base 2,043Wh + expansion batteries (up to 24,000Wh) covers your 8,600Wh need
Static answer (crawlable summary)
Typical device list: Window AC (12,000 BTU)×1, Router + Modem×1, Phone / Smartphone Charger×2.
Estimated from: Energy Star Certified Products · Mfr spec class: Netgear KB + measured (ARRIS SB8200) · Unbound Solar Power Table (secondary) — some household values are cross-checked class estimates (not single-model nameplates); check your own appliance nameplate before buying.
| Continuous load | 835 W |
|---|---|
| Startup peak | 2,435 W (driven by 1× Window AC (12,000 BTU)) |
| Daily energy use | 6,880 Wh |
| Recommended capacity | 8,600 Wh (25% margin included) |
| Minimum inverter | 920 W continuous |
💡 Optimization: switch to an inverter window AC
Modern inverter (variable-speed) window ACs — every currently ENERGY STAR-certified 12,000 BTU unit — ramp their compressor instead of slamming it on. Swap the standard unit in this scenario for an inverter/Most-Efficient one and the same engine computes:
| Standard unit | Inverter unit | |
|---|---|---|
| Startup peak | 2,435 W | 785 W |
| Daily energy | 6,880 Wh | 6,480 Wh |
| Battery needed | 8,600 Wh | 8,100 Wh |
Inverter units also have no locked-rotor startup surge — often the difference between a small station tripping and running fine. In real-world part-load conditions they often draw 300–600W, below the certified rated-point value we use.
Frequently asked questions
What size generator for window air conditioner?
For a typical setup (Window AC (12,000 BTU), Router + Modem and Phone / Smartphone Charger), you need at least 835W of continuous power. The single biggest moment is startup: when 1× window ac (12,000 btu) kicks on, the momentary draw peaks at 2,435W. For a full day of runtime we recommend at least 8,600Wh of battery capacity (your devices use about 6,880Wh per day, plus a 25% margin for a full day of use).
Which power stations can handle this?
Based on published specs, EcoFlow DELTA 3 Max Plus (with expansion batteries), EcoFlow DELTA Pro 3 (with expansion batteries), Jackery Explorer 2000 Plus (with expansion batteries) cover the 2,435W startup peak and deliver up to 1.5 days fully expanded / up to 1.8 days fully expanded / up to 3.5 days fully expanded of typical daily use. Check the comparison cards above for the full numbers.
Why is the startup surge higher than the running watts?
Motor-driven devices (fridge compressors, well pumps, air conditioners) draw 2-5× their running power for a split second at startup — measured as locked-rotor amps (LRA). On this page the biggest spike comes from the Window AC (12,000 BTU): a station that only meets the running load will trip or stall when it starts. Data sources: U.S. DOE Energy Saver, ENERGY STAR certified products, manufacturer spec sheets.