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An RV air conditioner is the biggest electrical load in most recreational vehicles and the main reason RV owners buy generators. Rooftop units range from about 11,000 to 15,000 BTU, with some ducted systems and dual units pushing demand much higher. Understanding running watts, the starting surge that trips small generators, and how heat and altitude affect draw helps you plan power for campgrounds, boondocking and travel days.
Typical RV air conditioner wattage
| RV AC size | Running watts | Starting watts (no soft start) | Starting watts (with soft start) |
|---|---|---|---|
| 11,000 BTU | ~1,000–1,200W | ~2,000–2,800W | ~1,400–1,800W |
| 13,500 BTU | ~1,200–1,700W | ~2,500–3,500W | ~1,600–2,200W |
| 15,000 BTU | ~1,400–1,900W | ~3,000–4,000W | ~1,900–2,500W |
| Two 13,500 BTU units | ~2,400–3,400W | ~3,700–5,200W (staggered start) | ~2,800–3,900W |
| Inverter/variable-speed rooftop | ~500–1,400W (modulating) | Minimal surge | N/A |
Why the starting surge matters
Most RV rooftop ACs use fixed-speed compressors that pull a large inrush current when starting — typically two to three times running watts for a fraction of a second. Small inverter generators can hit their overload limit during this surge even though running watts are well within capacity. Soft-start devices reduce this inrush by 50–70%, which is why they have become so popular among RV owners.
Factors that increase running watts
- Outdoor heat: above 90–95°F, compressors work harder and draw 10–20% more.
- Low voltage: weak campground pedestals or long cords can cause voltage drop, raising amperage and stress.
- Dirty filters and coils: restricted airflow increases draw and reduces cooling.
- Fan speed and mode: high fan adds 50–100W; fan-only mode uses around 100–300W.
- Altitude: thinner air affects cooling efficiency and generator output.
Daily energy use
The compressor cycles on and off with the thermostat. In moderate heat, a 13,500 BTU unit might run 50–60% of the time; in extreme heat with sun exposure, nearly continuously.
| RV AC (running ~1,500W) | Duty cycle | Energy per 8 hours | Energy per 24 hours |
|---|---|---|---|
| Mild day, shaded | ~40% | ~4.8 kWh | ~12 kWh |
| Hot day, partial shade | ~65% | ~7.8 kWh | ~19 kWh |
| Very hot, full sun | ~90% | ~10.8 kWh | ~26 kWh |
These totals show why running an RV AC from batteries alone requires very large lithium banks — often 5–10kWh or more — plus substantial solar or generator charging.
Checking your RV AC
The AC’s data plate, visible after removing the interior shroud or on the rooftop unit, lists rated amps and LRA. Multiply running amps by 120V for running watts; multiply LRA by 120V to estimate peak inrush. Many RV power management systems or smart surge protectors also display live amperage.
Reducing AC energy use
- Park in shade and orient the RV to minimize afternoon sun on large windows.
- Use reflective window covers and close blinds.
- Clean filters monthly during heavy use and inspect rooftop coils yearly.
- Pre-cool the RV in the morning and avoid running ovens or cooktops during peak heat.
- Install a soft starter to reduce surge and allow smaller generators.
30A versus 50A RVs
A 30A RV has about 3,600W available at 120V; a single AC plus a microwave can approach that limit. 50A RVs have two 120V legs totaling up to 12,000W, which supports two ACs and other appliances simultaneously.
Heat pump rooftop units
Some RVs use rooftop heat pumps that provide both cooling and heating. In cooling mode, their wattage is similar to standard rooftop ACs. In heat mode, they draw roughly 1,200–1,700W and work efficiently down to around 40°F, below which output drops and many owners switch to the propane furnace. Heat pump operation on generator power uses the same sizing as cooling, while furnace use needs only 50–150W for the blower and control board. Knowing which mode you will use helps you plan both generator capacity and fuel.
Battery-powered AC
Running a 13,500 BTU AC from a lithium bank for 4 hours at 60% duty needs about 3.5–4.5 kWh plus inverter losses. That typically means 400Ah or more at 12V (about 5 kWh) and a 3,000W inverter, which is why most RVers still rely on generators for sustained cooling.
FAQ
How many watts does a 13,500 BTU RV AC use?
Typically 1,200–1,700W running and 2,500–3,500W starting without a soft starter.
How many watts does an RV AC use on fan only?
Usually about 100–300W, depending on fan speed and model.
Bottom line
RV air conditioners typically draw 1,000–1,900W running with starting surges of 2,000–4,000W. Soft starters, shade and good maintenance reduce both surge and daily energy use, making it much easier to power your AC from a generator or battery system.
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