What Size Generator to Run An RV Air Conditioner
- How RV Air Conditioners Work and Why Generator Size Matters
- Key Factors That Determine Generator Size for RV AC
- Generator Size Recommendations by AC Unit Size
- Step-by-Step: How to Calculate the Right Generator Size for Your RV AC
- Special Considerations for RV Generator Sizing: Soft Starters, Amp Ratings & Generator Types
- Get the Right Generator for Your RV AC and Hit the Road Worry-Free
Choosing the right generator size for your RV air conditioner is crucial for comfortable and safe travel. An undersized generator won't handle the substantial power demands of your AC unit, potentially damaging both your generator and air conditioner while leaving you sweating in the summer heat. Most RV air conditioners require between 1,500-1,800 watts for continuous operation but need a much higher 2,800-3,500 watts during startup surge. Your specific needs will depend on your AC unit's BTU rating, with larger 15,000 BTU units requiring generators of at least 4,000 watts, while smaller 13,500 BTU units can operate with 3,000-watt generators. The right generator ensures your cooling system works flawlessly while allowing you to power additional appliances during your adventures.
How RV Air Conditioners Work and Why Generator Size Matters
RV air conditioners are founded upon the same principles of cooling as home units but are designed for mobile applications with various power requirements.
BTU Ratings Explained
BTU (British Thermal Unit) ratings define your RV air conditioner's capacity for cooling. Most RV air conditioners are between 9,000 and 15,000 BTUs, with 13,500 BTUs the most standard size. The higher the BTU rating, the more cooling capacity, but the more electricity it consumes. A 13,500 BTU unit will draw around 1,500 watts to operate continuously, and a 15,000 BTU unit around 1,800 watts. These ratings dictate the minimum generator size that will work with your particular air conditioner.
Starting Power vs. Running Power
Running wattage is the power required to keep your air conditioner operating once it's already on. For example, a 13,500 BTU air conditioner might require 1,500 watts to operate continuously. Starting wattage (or surge wattage) is the significantly higher amount of power that's needed for the first few seconds when the compressor starts up. This surge will be 2-3 times higher than the running wattage, typically 2,800-3,500 watts for most RV air conditioners. Your generator must handle this initial surge, or the air conditioner won't start.
Why Generator Size Really Matters
Selecting the right generator size is crucial for several reasons. An undersized generator won't provide the necessary surge wattage to initiate your air conditioner, resulting in unsuccessful starts or generator shutdown. This has the potential to ruin both your air conditioner and generator in the long run. Secondly, most RVers require powering several appliances at once. Your generator has to support not just the air conditioner but other appliances such as refrigerators, microwaves, and charging systems. Sizing properly allows all your appliances to work appropriately without overwhelming your power supply.
Handling Power Spikes and Daily Usage
Startup surge is the biggest challenge in powering an RV air conditioner. Even though a 13,500 BTU air conditioner might only need 1,500 watts to run, its startup surge might be 3,000 watts or more. That means that a 2,000-watt generator that seems adequate by running wattage alone won't start the air conditioner. Generators should be sized to the highest potential power demand, typically the startup surge of the air conditioner and the running wattage of other essential appliances. This will ensure your electrical system operates reliably under all conditions.
Key Factors That Determine Generator Size for RV AC
The right generator size depends not just on your air conditioner's specifications, but also on your RV's overall electrical system and how you use your appliances.
AC Unit Size and Power Requirements
Different BTU ratings equate to different power requirements. A 9,000 BTU air conditioner will take about 900-1,000 watts to run and 1,800-2,000 watts to start. 11,000 BTU units need about 1,100-1,200 running watts and 2,200-2,400 starting watts. Standard 13,500 BTU air conditioners need 1,500-1,700 running watts and 3,000-3,500 starting watts. Large 15,000+ BTU units need 1,800-2,000 running watts and 3,600-4,000 starting watts. These are key requirements when sizing your generator relative to your air conditioning needs.
Number of AC Units
Most bigger RVs have two air conditioners, doubling power requirements. A twin 13,500 BTU installation takes approximately 3,000-3,400 running watts, but the question is whether the two units could conceivably start at the same instant, temporarily drawing 6,000-7,000 watts. Even if you start them staggered, your generator will need to supply at least one AC starting and one running constantly. It generally takes a 5,000+ watt generator to run two AC units smoothly.
Other Appliances
Your air conditioner is not the only electrical power guzzler in your RV. Standard appliances are microwaves (1,000-1,500 watts), electric coffee makers (600-1,200 watts), refrigerators (400-1,000 watts running, 600-1,200 to start), electric water heaters (1,000-1,500 watts), and smaller ones like lights (20-100 watts), TVs (100-400 watts), and device chargers (25-100 watts). Your total simultaneous load—what you'll actually use at the same time—will determine your actual generator size requirement.
RV Electrical System
Your RV electrical system plays an important role in determining generator size. A 30-amp system can safely accommodate up to 3,600 watts (30 amps × 120 volts) total, so a 3,000-4,000-watt generator will usually suffice. A 50-amp system can safely carry up to 12,000 watts (50 amps × 240 volts) and possibly necessitate a bigger 5,000-7,000-watt generator to maximize the system's capacity. Your generator needs to be sized for your RV's electrical system to prevent underusing or overloading your equipment.
Environmental Factors
Generator output is lower at high elevations and in very hot or very cold temperatures. Generators lose approximately 3.5% of their rated power for each 1,000 feet above 3,000 feet of altitude. On the other hand, extremely warm temperatures (over 90°F) reduce generator efficiency by 10-15%. If you camp frequently in high-altitude or very warm locations, make your generator 15-20% larger than your calculated load to compensate for these environmental factors.
Soft Starters
Soft starters have the potential to reduce your generator size requirements by reducing the startup surge on the air conditioner by 50-65%. Instead of needing 3,000-3,500 start watts to drive a 13,500 BTU air conditioner, a soft starter might be able to reduce that to 1,800-2,000 watts. That would make a 2,200-watt generator big enough to drive a 13,500 BTU air conditioner, which would require a 3,000+-watt generator otherwise. The cost of installing a soft starter ($300-$400) might be cheaper compared to purchasing a larger generator.
.png)
.png)
Generator Size Recommendations by AC Unit Size
Enough with the theory—let's talk specific numbers. If you're wondering "What size generator do I need for my 13,500 BTU air conditioner?" or any other common RV AC unit, this table has you covered with clear recommendations.
AC Unit Size (BTU) | Running Wattage | Starting Wattage | Recommended Generator Size |
9,000 | ~950 W | ~1,700 W | 2,000 W |
11,000 | ~1,250 W | ~2,300 W | 2,500 W |
13,500 | ~1,500 W | ~2,800 W | 3,000 W |
15,000 | ~1,800 W | ~3,500 W | 4,000 W |
Dual 13,500 | ~3,000 W | ~5,600 W | 6,000 W+ |
Why You Should Always Size Up, Never Down:
A generator that's a bit too large will work perfectly fine at partial power
Running at partial capacity is actually easier on your generator's engine
Many generators are more fuel-efficient when not maxed out
A generator that's too small will either fail to start your AC or shut down from overload●
Repeatedly overloading a generator can damage both the generator and your expensive AC unit
This guide only covers your air conditioner's power needs. For real camping situations, you need to add the wattage of other appliances you'll use at the same time. If you have a 13,500 BTU air conditioner (needing a 3,000W generator) and want to run your 1,200W microwave while the AC is on, you should get a 4,000W+ generator for reliable power without overloads.
Step-by-Step: How to Calculate the Right Generator Size for Your RV AC
Finding the perfect generator size doesn't have to be complicated. Follow these six simple steps to ensure you get a generator that reliably powers your RV air conditioner and other appliances without overloading:
Step 1: Find your AC's running and starting wattage
Look for this information in your air conditioner's owner manual or on the specification label (usually located on the side or back of the unit). If you can't find it, refer to the table above for estimates based on BTU rating, or contact the manufacturer with your model number.
Step 2: List all other appliances you plan to run simultaneously
Make a complete list of everything you might run at the same time as your AC. Common RV appliances include:
Microwave (600-1,200W)
Coffee maker (600-1,200W)
Electric water heater (1,000-1,500W)
Refrigerator (400-1,000W)
TV/entertainment system (100-400W)
Laptop charger (45-90W)
Phone chargers (5-20W each)
Step 3: Add up all running wattages
Total the continuous power needs of all devices. For example:
13,500 BTU AC: 1,500W
Refrigerator: 600W
TV: 150W
Two phone chargers: 30W
Total running wattage: 2,280W
Step 4: Add the highest starting wattage
Your air conditioner typically has the highest starting surge. For a 13,500 BTU unit, this might be an additional 1,300W above its running wattage. Add this to your total:
Total running wattage: 2,280W
AC starting surge: 1,300W
New total: 3,580W
Step 5: Add a 20-25% safety margin
Generators should not run at maximum capacity for extended periods. Add 20-25% to ensure reliable operation and extend your generator's life:
Total with starting wattage: 3,580W
With 20% safety margin: 4,296W
Step 6: Choose a generator that meets or exceeds this total
Round up to the nearest available generator size. In this example, you would need at least a 4,500W generator for reliable operation.
Remember: Altitude, temperature, and generator age can all reduce actual power output. When in doubt, choose the larger option to ensure you're never left without power when you need it most.
Special Considerations for RV Generator Sizing: Soft Starters, Amp Ratings & Generator Types
Using a Soft Starter for Your RV Air Conditioner
What Is a Soft Starter and How Does It Work?
A soft starter is an electronic device that slowly eases the load off your RV electrical system as the air conditioner compressor initially comes on. Instead of taking a massive power surge all at once, the soft starter ramps up the power smoothly, reducing the initial spike by 60-70%. It does this by controlling the voltage fed to the motor during startup so that it ramps up smoothly rather than abruptly.
Dramatically Reduce Your Generator Size Requirements
The best benefit of installing a soft starter is that it will reduce your generator size needs by up to 70% for that critical startup period. Without a soft starter, your generator must deal with the running wattage plus the massive startup surge. With a soft starter installed:
The starting surge drops from 3,000-3,500W to just 1,000-1,200W
Your total generator requirement may decrease by 1,500-2,000W
You can potentially use a smaller, lighter, quieter, and less expensive generator
Running a 13,500 BTU AC with a 2,000W Generator
Without a soft starter, a typical 13,500 BTU air conditioner requires a 3,000-3,500W generator to handle the startup surge. After installing a quality soft starter:
The same 13,500 BTU air conditioner can reliably start and run on a 2,000W inverter generator
This allows popular models like the Honda EU2200i or Yamaha EF2200iS to power your AC
Many RVers report successful operation even in hot weather conditions
30-Amp vs. 50-Amp RVs
Typical Generator Size Ranges for Each
30-AmpRV Systems:
Maximum theoretical power: 3,600 watts (30A × 120V)
Recommended generator size: 2,800-3,500 watts
Ideal for smaller RVs with single AC units and basic appliances
50-AmpRV Systems:
Maximum theoretical power: 12,000 watts (50A × 240V)
Recommended generator size: 4,000-7,500 watts
Necessary for larger RVs with multiple AC units, residential refrigerators, and other power-hungry appliances
For those with dual air conditioners and luxury appliances, the EcoFlow Power Kits 5kVA 48V Power System delivers impressive performance with 4000W continuous output and 8000W surge capacity—enough to run two 13,500 BTU air conditioners simultaneously plus other high-draw appliances like air fryers and space heaters without requiring soft starters.
Compatibility and Safety Tips
Never exceed your RV's electrical system rating with an oversized generator
For 30-amp RVs, ensure your generator has a 30-amp RV outlet or use an appropriate adapter
For 50-amp RVs, a smaller generator can still work if you manage loads carefully
Use a surge protector/energy management system to prevent overloads
Monitor your power distribution panel to ensure you're not exceeding circuit capacities
Consider installing an automatic transfer switch for seamless transitions between power sources
Portable vs. Onboard Generators
Pros and Cons of Each Type
Pros: Lower initial cost, can be used away from the RV, easier to service/replace, can be stored when not needed
Cons: Must be manually set up, exposed to elements, potential theft risk, takes up storage space, typically louder
Onboard Generators:
Pros: Integrated into RV systems, auto-start capability, protected from weather and theft, often quieter, fuel drawn directly from RV tank
Cons: Higher initial cost, adds weight to RV, more complex installation and repairs, cannot be used away from the RV
When to Choose One Over the Other
Choose a Portable Generator When:
You camp primarily at locations with hookups and only occasionally need generator power
You're on a tighter budget
You want flexibility to use the generator for other purposes
You have limited space in your RV for a built-in unit
You prefer to upgrade your generator technology more frequently
Choose an Onboard Generator When:
You frequently boondock or dry camp
You value convenience and automation
You have multiple power-hungry appliances
You have physical limitations that make setting up a portable generator difficult
You prefer an integrated solution that doesn't require separate storage
Get the Right Generator for Your RV AC and Hit the Road Worry-Free
Selecting a generator for your RV air conditioner is easier than you might imagine. Begin by calculating your AC's running watts plus its starting surge, and then add any other appliances you will use simultaneously. Always add a little extra, around 20%—this keeps your generator from running at full capacity all the time. Consider putting a soft starter in to slice your power demands in half--many RVers can run a 13,500 BTU air conditioner using just a 2,000-watt generator with this simple modification! An on-the-move unit for simplicity or a built-in generator for convenience is dependent on your boondocking style and budget.