How Many Watts Does an RV AC Use?
ZacharyWilliamRV Power & Cooling • Practical electrical sizing for real-world camping
Most rooftop RV air conditioners run around 1,200–2,000 watts while actively cooling, but they can demand a much higher startup surge (often several thousand watts) for a very short moment when the compressor kicks on.
The fastest way to get the right number for your rig is to check your AC’s label (or manual) for amps, then convert amps to watts (examples below).
Quick Answer (Typical Watt Ranges)
In most U.S. RVs, a rooftop AC runs on 120V AC. When it’s cooling (compressor running), you’ll often see something like 10–16 amps, which converts to roughly 1,200–2,000 watts.
| RV AC Type / Size | Typical Running Power | Startup Surge (Momentary) | What to Know |
|---|---|---|---|
| 11,000–13,500 BTU rooftop (non-inverter) | ~1,300–1,900 W | Often “feels like” 6,000–9,000 W+ equivalent | High startup is the main reason small inverters/power stations struggle. |
| 15,000 BTU rooftop (non-inverter) | ~1,500–2,000 W | Similar surge issue; sometimes higher due to compressor LRA | Hotter weather = longer compressor run time and higher average draw. |
| Variable-speed / “inverter” rooftop AC | Varies widely; can be much lower at partial load | Often reduced vs traditional units | Check the nameplate and test with a meter—marketing varies by model. |
Real-World Examples From Rooftop AC Specs
Below are example electrical ratings (compressor + fan) pulled from a rooftop RV AC installation manual table. These are great for building a realistic expectation before you size shore power, a generator, or a battery system.
| Example Model Class | Cooling (BTU/hr) | Compressor RLA (A) | Fan RLA (A) | Estimated Running Watts @120V | Compressor LRA (A) | Estimated Startup “Equivalent Watts” @120V | Manual’s Min Generator Guidance |
|---|---|---|---|---|---|---|---|
| Rooftop AC example | 11,000 | 11.5 | 2.6 | ~1,692 W ( (11.5+2.6)×120 ) | 55.0 | ~6,600 W (55×120), plus fan inrush | 3.5 kW (1 unit) / 5.0 kW (2 units) |
| Rooftop AC example | 13,500 | 12.4 | 2.5 | ~1,788 W ( (12.4+2.5)×120 ) | 63.0–68.0 | ~7,560–8,160 W (LRA×120), plus fan inrush | 3.5 kW (1 unit) / 5.0 kW (2 units) |
| Rooftop AC example | 15,000 | 13.3 | 2.0 | ~1,836 W ( (13.3+2.0)×120 ) | 66.0–70.0 | ~7,920–8,400 W (LRA×120), plus fan inrush | 3.5 kW (1 unit) / 5.0 kW (2 units) |
“RLA” = Rated Load Amps (typical running current). “LRA” = Locked Rotor Amps (startup/inrush reference point). Startup demand is brief, but it’s the sizing bottleneck for many portable power solutions.
How to Calculate RV AC Watts From Amps
If your RV AC label lists amps, you can estimate watts with: Watts ≈ Volts × Amps (for most RV rooftop units, volts are typically ~120V).
| If Your AC Draws… | At ~120V, That’s About… | What That Means |
|---|---|---|
| 10A while cooling | ~1,200W | Often a smaller unit, partial load, or a high-efficiency design. |
| 13A while cooling | ~1,560W | A common real-world number for many rooftop units. |
| 16A while cooling | ~1,920W | Heavier load conditions (heat, low voltage, dirty coils/filters). |
Why Your RV AC Wattage Changes
Even with the same AC model, the watts you see can swing a lot. Common reasons:
- Outdoor temperature & sun exposure: hotter roof + direct sun = longer compressor runtime.
- Voltage drop at the pedestal: lower voltage often increases current draw for the same work.
- Altitude and airflow: restricted airflow (dirty filter/coils) makes the system work harder.
- Other RV loads: battery charger/converter, microwave, water heater, and fridge can overlap with AC draw.
- Compressor cycling: average watts over an hour can be far less than “compressor on” watts.
30A vs 50A Shore Power: What It Means for AC
Your shore power service limits how many high-draw loads you can stack with the AC. Here’s the simplest way to think about it.
| Service | Common RV Interpretation | Approx Max Power | Real-World AC Implication |
|---|---|---|---|
| 30A | Single 120V leg | ~3,600W (30A×120V) | One AC is usually fine, but avoid stacking microwave + electric water heater + AC. |
| 50A | Two 120V legs (split service) | Up to ~12,000W total available | More headroom for two ACs and other loads (still depends on your RV’s distribution panel). |
Can a Battery/Power Station Run an RV AC?
Step 1: Compare Your AC to the Power Source
| What to Check | Rule of Thumb | Why It Matters |
|---|---|---|
| Running watts | Power source continuous rating should exceed running watts with headroom | Prevents overload shutdown during sustained cooling. |
| Startup surge / inrush | Power source must handle compressor start (or you need a soft-starter) | This is the #1 reason AC won’t start on small inverters. |
| Energy capacity (Wh) | Higher Wh = longer runtime; AC is one of the fastest ways to drain a battery | Even if it starts, it may only run for a short window. |
Step 2: Understand the “Hours of Runtime” Math
A simple estimate: Runtime (hours) ≈ Battery (Wh) × 0.85 ÷ Load (W) where 0.85 is a practical efficiency placeholder for inverter losses and real-world conditions.
UDPOWER examples (battery-only estimates)
These are math estimates, not a promise of compatibility. Motor loads (like AC compressors) can require much higher startup power than their running watts.
| UDPOWER Model | Battery Capacity | AC Output Rating (as listed) | ~600W Load | ~900W Load | ~1200W Load | What This Usually Covers Well |
|---|---|---|---|---|---|---|
|
S1200 (product page)  |
1191Wh | 1200W (1800W max), 5 AC outlets | ~1.69 hrs | ~1.12 hrs | ~0.84 hrs | Fans, electronics, small appliances; AC may be possible only in select low-surge scenarios. |
|
C600 (product page)  |
596Wh | 600W (1200W max), 2 AC outlets | ~0.84 hrs | ~0.56 hrs | ~0.42 hrs | Charging, laptops, small devices; typically not intended for starting a rooftop RV AC. |
Solar input can extend time (when conditions allow)
| UDPOWER Model | Max Solar Input (as listed) | Practical takeaway |
|---|---|---|
| S1200 | 400W max (12–75V, 12A) | In strong sun, solar can offset part of the load, but AC still drains quickly. |
| C600 | 240W max (11–28V, 8.2A) | Helpful for “daytime support” loads; AC is still a high-demand use case. |
If your real goal is “stay comfortable off-grid,” many RVers pair efficient airflow (roof vent fans + shade + insulation) with short, strategic AC runs on shore/generator. For lighter RV tasks (charging and essentials), smaller stations like UDPOWER C400 can still be useful—just don’t expect it to start a rooftop AC.
Ways to Reduce AC Power Demand
- Install a soft starter (if compatible): some soft starters advertise up to ~75% reduction in startup current, which can be the difference between “won’t start” and “starts reliably.”
- Clean filters and coils: restricted airflow raises amperage and reduces cooling performance.
- Manage voltage drop: use a proper shore cord, avoid loose adapters, and consider a quality surge/voltage monitor.
- Pre-cool and shade: reflective windshield covers, awnings, and parking orientation can reduce run time.
- Don’t stack high loads: microwave, electric water heater, and space heaters compete with AC on 30A service.
FAQ
1) How many watts does a 13,500 BTU RV AC use?
Many 13.5k rooftop units run around ~1,300–1,900W while cooling, but startup surge can be much higher for a moment. Your exact wattage depends on the model and conditions—check the data plate for amps.
2) How many watts does a 15,000 BTU RV AC use?
Commonly ~1,500–2,000W while cooling, with a brief higher startup surge. Heat, humidity, and voltage drop can increase average draw.
3) Why is RV AC startup wattage so high?
The compressor can draw a large inrush current at startup (often referenced by “LRA” on spec sheets). That surge is brief, but it’s the hardest moment for inverters and small generators.
4) Can I run my RV AC on 30 amp shore power?
Usually yes for one AC—just avoid stacking other big loads at the same time (microwave, electric water heater, etc.).
5) Can I run two RV ACs on 30 amp?
It’s often unreliable. Even if they start, the combined running watts plus other RV loads can trip breakers. Two ACs is typically a 50A-service scenario (or careful energy management).
6) What’s the most accurate way to measure my RV AC watts?
Use an AC power meter (or clamp meter + voltage reading) while the compressor is running. Measuring at the pedestal or with an inline meter can also show total RV draw.
7) Does a soft starter guarantee my AC will run on a battery?
No. It can reduce startup demand, but you still need enough continuous watts to keep the compressor running and enough battery (Wh) for runtime.
8) Why does my AC trip the breaker at some campgrounds but not others?
Voltage drop, shared pedestal load, poor connections, or simultaneously running other appliances can push you over the limit.
9) Does “BTU to watts” conversion tell me electrical watts?
Not directly. BTU/hr describes cooling output (heat moved). Electrical input watts depend on efficiency. Use the data plate amps for the most accurate electrical estimate.
10) If I can’t run the AC, what’s a practical backup plan?
Many RVers combine airflow (vent fans), shade, reflective covers, and short “cool-down” cycles on shore or generator. A portable power station is often most effective for essentials and electronics rather than continuous AC.
Sources & Further Reading
- Rooftop AC electrical ratings and generator sizing table (installation manual): Dometic rooftop AC installation PDF (hosted copy)
- Amps to watts relationship: Electrical Safety First: Amps × Volts = Watts
- Soft-starter concept (startup current reduction claim): Micro-Air EasyStart Breeze (soft starter)
- 30A vs 50A RV service overview: Camping World: 30A vs 50A differences
- UDPOWER product references used in the runtime examples: UDPOWER S1200, UDPOWER C600, UDPOWER C400
Written by an RV power & enerACgy-use researcher who focuses on translating manufacturer specs (amps, LRA/RLA, watt-hours) into practical sizing guidance for shore power, generators, and portable battery systems.
Editorial note: Always verify your specific AC model’s label/manual and test under your real conditions (temperature, voltage, altitude).RV
