What Size Generator Do You Need for an RV Air Conditioner?

Most RV owners need a generator rated for approximately 3,000 to 4,500 starting watts to run one rooftop air conditioner reliably.

A 13,500 BTU RV air conditioner will often work with a generator providing about 3,000 to 3,200 starting watts and at least 2,500 to 2,600 running watts. A 15,000 BTU air conditioner is better matched to a 3,500- to 4,500-watt generator, particularly if you want to power other appliances.

A 2,000-watt generator may run certain efficient RV air conditioners with a properly installed soft starter, but it should not be treated as a universal solution. The exact air-conditioner model, compressor starting demand, elevation, temperature, fuel type, and other active appliances all affect the result.

RV owners who want to avoid engine noise and fuel storage can also consider a battery-based alternative. Our guide to the best portable power stations for RV air conditioners compares inverter output, battery capacity and realistic cooling runtime.

Check our RV Generator Wattage Calculator for your RV appliances.

Quick RV Air-Conditioner Generator Size Chart

These recommendations provide a practical starting point. Always check the electrical label and documentation for your exact air conditioner.

If you would rather avoid engine noise and exhaust, compare these requirements with the output and runtime needed to run an RV air conditioner from a portable power station.

Generator advertising can make these numbers confusing. A generator described as a “4,500-watt generator” may produce only 3,500 running watts. Always compare both ratings.

Starting watts cover brief power surges, such as an air-conditioner compressor turning on.

Running watts are the power the generator can supply continuously.

For RV use, both numbers matter.

Why RV Air Conditioners Are Difficult to Start

An air conditioner does not draw the same amount of power all the time.

After the compressor is running, a typical rooftop unit may consume roughly 1,300 to 1,800 watts under moderate conditions. Certain models can use more in high temperatures or other demanding conditions. One Coleman-Mach service manual, for example, lists 1,710 cooling watts under standard conditions and as much as 2,150 watts under its stated maximum test condition.

The compressor requires a brief but much larger surge when it starts. That surge is why an air conditioner that normally consumes 1,500 watts may overload a small generator during startup.

Manufacturer specifications demonstrate how significant the difference can be. One Dometic specification sheet lists a 13,500 BTU model at 12.5 full-load cooling amps but 63 locked-rotor amps. Locked-rotor current cannot simply be converted into a portable-generator recommendation, but it illustrates how much more demanding compressor startup can be than normal operation.

The generator must therefore handle:

• The air conditioner’s normal running load
• The compressor’s starting surge
• Every other appliance already operating
• A reasonable margin for changing conditions

A generator that barely starts an air conditioner during a cool test at home may not do so as reliably at a hot, high-elevation campsite.

Generator Size for a 13,500 BTU RV Air Conditioner

For most conventional 13,500 BTU rooftop air conditioners, a generator with approximately 3,000 to 3,200 starting watts and at least 2,500 to 2,600 running watts is a sensible minimum.

This size works best when the air conditioner receives priority. Turn off the microwave, coffee maker, electric water heater, and other major loads before starting it.

Honda specifically states that its 3,200-watt EU3200i can run most 13,500 BTU RV air conditioners. Its 2,600-watt continuous rating is equally important, however, because that determines how much equipment it can keep running after the compressor starts.

For a closer look at this particular setup, see Can the Honda EU3200i Run a 13,500 BTU RV Air Conditioner?

A 3,500- to 4,500-watt inverter generator provides more flexibility. The extra capacity may allow the air conditioner to run alongside a battery converter, refrigerator, lights, television, and device chargers without operating at the generator’s limit.

If you regularly camp in extreme heat, use propane, travel at higher elevations, or do not have a soft starter, moving up to the 4,500-watt class is the safer choice.

Generator Size for a 15,000 BTU RV Air Conditioner

A 15,000 BTU rooftop air conditioner generally calls for a generator in the 3,500- to 4,500-watt range.

The required wattage can sometimes be supplied by two compatible generators operating in parallel rather than one larger unit. Compare two small inverter generators versus one large generator before deciding which configuration to buy.

Some 15,000 BTU units may start on a smaller generator, especially with a soft starter. That does not make a smaller generator dependable for every model or campsite.

A 4,500-watt generator is usually the more practical choice because it offers:

• More compressor-starting capacity
• Additional running-watt headroom
• Better performance when using propane
• More flexibility for the converter and refrigerator
• Less need to operate near maximum output

Even at this size, the microwave, electric water heater, toaster, hair dryer, or coffee maker may push the total load too high. One high-wattage appliance should generally be used at a time while the air conditioner is operating.

Our guide to the Best Quiet 4500-Watt Inverter Generators for RV Air Conditioners examines the strongest options for this use.

Can a 2,000-Watt Generator Run an RV Air Conditioner?

Sometimes—but only under the right conditions.

A 2,000-watt generator may run:

• A smaller 5,000- to 8,000 BTU air conditioner
• Certain high-efficiency rooftop units
• Some 13,500 BTU models equipped with a compatible soft starter
• An air conditioner with nearly all other RV loads turned off

The problem is that many generators in this class provide only about 1,600 to 1,800 continuous watts. That leaves very little capacity after the air conditioner begins running.

The converter may automatically start charging the battery. The refrigerator may be using electric power instead of propane. A fan, television, or other seemingly small load may use the remaining capacity.

A 2,000-watt generator is therefore a specialized, lightweight solution—not the safest general recommendation for a conventional 13,500 or 15,000 BTU rooftop air conditioner.

If portability matters more than running a large AC, see our guide to the Best Quiet 2000–2500W Inverter Generators for Camping.

How Much Power Can Run With the Air Conditioner?

Sizing the generator for the air conditioner alone is only half the calculation. The more useful question is what can operate simultaneously.

The following examples use estimated loads. Your RV’s actual appliances may differ.

Example 1: 13,500 BTU AC on a 3,200-Watt Generator

Assume the generator produces 3,200 starting watts and 2,600 running watts.

This combination leaves approximately 700 running watts available. It does not leave enough room for most microwaves, coffee makers, or electric water heaters.

The converter can also draw more when the RV battery is heavily discharged. Turning it off temporarily may help the air conditioner start.

Our What Can a Honda EU3200i Run? RV and Home-Backup Wattage Guide includes additional simultaneous-load examples.

Example 2: 15,000 BTU AC on a 4,500-Watt Generator

Assume the generator produces 4,500 starting watts and 3,500 running watts.

This leaves about 1,000 watts under the generator’s continuous rating.

That still may not be enough for a microwave whose electrical input is 1,200 to 1,500 watts. The number printed on a microwave’s front is often its cooking output—not necessarily the amount of electricity it draws.

Temporarily switching the refrigerator to propane and reducing converter demand can create more usable headroom.

Example 3: Two Rooftop Air Conditioners

Suppose one air conditioner consumes 1,500 watts and the second consumes 1,700 watts.

The continuous load appears manageable for some generators, but starting the compressors is the difficult part. The units should not start simultaneously.

A generator with approximately 5,500 to 7,000 running watts may handle two air conditioners with load management, while a 7,000- to 8,500-watt model provides a more useful buffer. Exact compatibility still depends on both AC units and the generator’s motor-starting capability.

How to Calculate the Generator Size Your RV Needs

You can estimate the required generator size in four steps.

1. Find the Air Conditioner’s Electrical Specifications

Check the AC data plate, owner’s manual, or manufacturer documentation for:

• Rated voltage
• Compressor amps
• Fan amps
• Full-load amps
• Locked-rotor amps
• Recommended generator size
• Whether a factory soft-start system is installed

BTU tells you the unit’s cooling capacity. It does not tell you its exact electrical demand. Two 13,500 BTU air conditioners can have different startup and running requirements.

2. Calculate the Running Load

If the appliance provides amps but not watts, use:

Watts = Volts × Amps

For example:

120 volts × 12.5 amps = 1,500 watts

This is a useful basic estimate. Motors and alternating-current equipment introduce additional factors, so the manufacturer’s published wattage or generator recommendation should take priority when available.

Add the running watts of everything you plan to use at the same time.

3. Account for the Largest Starting Surge

Do not simply add every appliance’s possible starting demand together. Most of them will not start at exactly the same moment.

Instead, add your total running load to the largest additional starting requirement among the motor-driven appliances. Generac uses this same general method in its portable-generator sizing guidance.

Remember that the air-conditioner compressor cycles. It can restart while the refrigerator, converter, or television is already operating.

4. Add Operating Headroom

Avoid choosing a generator that matches your calculation exactly. Extra capacity helps accommodate:

• Higher outdoor temperatures
• High-elevation power loss
• Propane operation
• Battery charging
• Compressor cycling
• Normal variations between appliances
• Generator aging and maintenance condition

For RV air-conditioning use, several hundred watts of unused continuous capacity can make a noticeable difference.

Will a Soft Starter Let You Use a Smaller Generator?

A soft starter can substantially reduce the compressor’s startup current. It does not meaningfully eliminate the air conditioner’s normal running load.

Micro-Air says its EasyStart products can reduce startup current by as much as 75%. The actual result depends on the air conditioner, installation, generator, and operating conditions.

A soft starter may:

• Help a marginal generator start the compressor
• Reduce voltage sag during startup
• Make a 2,000- to 3,000-watt generator practical with certain AC units
• Improve starting reliability at difficult campsites
• Make it easier to run two AC units with load management

It will not create additional continuous wattage. If the air conditioner and other appliances require 2,500 running watts, a generator limited to 1,800 running watts remains undersized.

A soft start can reduce the brief compressor surge that often determines whether a smaller inverter generator can start an RV air conditioner. It does not significantly reduce the A/C’s continuous running load, however, and it cannot restore generator output lost to high elevation or extreme heat. The effect also differs between 13,500 and 15,000 BTU systems. See our complete RV Air Conditioner Soft Start Guide for starting amps, before-and-after generator ranges, environmental limitations and hardwired versus plug-and-play options.

A soft starter should also not be confused with a simple hard-start capacitor. The products manage compressor startup differently.

Check AC compatibility and installation requirements before purchasing. Improper installation can damage equipment or create an electrical hazard.

Conditions That Can Reduce Available Generator Power

A generator and air conditioner may work during one trip but struggle during another. Several variables can explain the difference.

High Elevation

Naturally aspirated generator engines lose power as elevation increases. Honda manuals commonly state that engine horsepower decreases by approximately 3.5% for every 1,000-foot increase in elevation, even with the appropriate high-altitude carburetor modification.

At 5,000 feet, the reduction can be significant. A generator with minimal capacity at sea level may no longer start the air conditioner reliably in the mountains.

Follow the generator manufacturer’s high-altitude instructions rather than modifying the carburetor yourself.

Generator output decreases as elevation increases, so use our generator altitude derating calculator before choosing a generator for a high-elevation campground.

Extreme Heat

High outdoor temperatures make the air conditioner work harder. Compressor pressure and electrical demand can rise, while a hot generator may also have less favorable operating conditions.

If you camp regularly in desert climates, choose more generator headroom than a cool-weather calculation suggests.

Propane Operation

Dual-fuel generators commonly produce fewer running watts on propane.

For example, one current Champion 4,500-watt dual-fuel inverter is rated for 3,250 running watts on gasoline but 2,925 on propane. Another Champion model produces 3,500 running watts on gasoline and 3,150 on propane.

Use the propane rating when that is the fuel you intend to carry. Do not size the system using the higher gasoline number.

A Discharged RV Battery

The RV converter may draw substantial power when charging a depleted battery. This invisible load is a common reason an AC struggles to start even though no large appliance appears to be running.

Temporarily disabling the converter—or charging the battery before testing—can help identify the problem.

Eco Mode

Eco mode allows an inverter generator to slow its engine under light loads. Some generators respond to compressor startup quickly; others may hesitate or overload.

If the AC struggles to start, follow the generator manual and test with economy mode turned off. It can often be enabled again after the compressor is running.

Does a 30-Amp or 50-Amp RV Determine Generator Size?

The RV’s shore-power rating establishes its maximum available electrical service. It does not tell you how large a generator you need for one appliance.

A 30-amp RV connection provides a maximum of:

30 amps × 120 volts = 3,600 watts

A 50-amp RV connection normally provides two 50-amp, 120-volt legs, allowing as much as 12,000 watts across the complete service.

That does not mean every 30-amp RV needs a 3,600-watt generator or every 50-amp RV needs a 12,000-watt generator. You only need enough power for the appliances you intend to operate.

Also verify:

• The generator’s continuous wattage
• The amperage limit of its RV or locking outlet
• Whether the generator supplies 120 volts or 120/240 volts
• The rating of every adapter and cord
• Whether both sides of a 50-amp RV panel receive power through the chosen adapter

An outlet that physically fits a 30-amp RV cord does not increase the generator’s capacity.

Inverter or Conventional Generator for an RV Air Conditioner?

Both designs can run an RV air conditioner when properly sized, but an inverter generator is usually the better camping choice.

Inverter generators typically offer:

• Quieter low-load operation
• Lower fuel consumption when demand is reduced
• Cleaner power for electronics
• Smaller and more portable enclosed designs
• Parallel capability on certain models

Two smaller inverter generators can supply enough combined starting capacity for an RV air conditioner, but only when the manufacturer approves the exact generator combination and parallel equipment. See our guide to paralleling two inverter generators for compatibility rules, usable-wattage calculations and the effect of running two engines on noise.

A conventional generator may provide more wattage for the money, but it is often substantially louder. Noise matters at campgrounds, especially when the generator runs for several hours to keep the RV cool.

See our Best Quiet Inverter Generators for RV Camping for options that balance air-conditioner capacity with campground-friendly operation.

RV Generator Safety

Never operate a portable generator inside an RV, storage compartment, truck bed with a cover, garage, or other enclosed area. A portable generator should not be installed in an RV’s built-in generator compartment unless it was specifically designed and approved for that application.

The CDC says portable generators should be operated outdoors more than 20 feet from windows, doors, and vents. Direct the exhaust away from your RV and neighboring campsites, and use working battery-powered or battery-backup carbon-monoxide detectors inside the RV.

A CO-shutoff sensor is an important additional safeguard, but it does not make unsafe placement acceptable.

Keep the generator dry, follow its grounding instructions, and use cords and adapters rated for the full electrical load.

Frequently Asked Questions

Will a 3,500-watt generator run an RV air conditioner?

A generator with 3,500 starting watts can often run a 13,500 BTU RV air conditioner, provided its continuous rating is sufficient and other major loads are controlled. Check whether “3,500 watts” refers to starting or running output.

It may also run certain 15,000 BTU units, but compatibility is less certain without knowing the AC’s startup demand.

Will a 4,500-watt generator run a 15,000 BTU RV AC?

A 4,500-watt generator is usually a strong match for one 15,000 BTU rooftop air conditioner. A model offering about 3,200 to 3,500 running watts should also have room for essential RV loads, although high-wattage cooking and heating appliances still require load management.

Can I run the microwave and RV air conditioner together?

It depends on the generator’s continuous rating.

An AC drawing 1,600 watts and a microwave drawing 1,400 input watts already require approximately 3,000 watts. Adding the converter, refrigerator, and other loads may overload a 3,000- or 3,500-watt generator.

The simplest practice is to turn off the air conditioner temporarily while using the microwave.

Can I run a coffee maker while the AC is on?

A typical coffee maker may consume approximately 800 to 1,500 watts. A 4,500-watt generator may handle it alongside one air conditioner, depending on the remaining loads. A 3,000- or 3,200-watt generator generally requires more careful management.

Remember that the compressor can restart while the coffee maker is heating.

Is a soft starter necessary with a 4,500-watt generator?

Usually not for a single conventional 13,500 BTU air conditioner, but it can still improve startup behavior. It may be more valuable with a 15,000 BTU unit, high-elevation camping, propane operation, or a generator with limited surge capacity.

Can I parallel two smaller inverter generators?

Yes, if both generators and the parallel equipment are approved by the manufacturer for that configuration. Parallel operation can provide more capacity while allowing each generator to remain portable.

Do not connect generators together using homemade cables or unapproved methods.

The Bottom Line

For one 13,500 BTU RV air conditioner, begin with approximately 3,000 to 3,200 starting watts and at least 2,500 to 2,600 running watts. Move up to a 3,500- or 4,500-watt class if you want more flexibility.

For one 15,000 BTU air conditioner, a 4,500-watt inverter generator is the most practical general recommendation.

A 2,000-watt generator may work with a small or efficient air conditioner—or with certain rooftop units equipped with a soft starter—but it is not a dependable answer for every RV.

For two rooftop air conditioners, expect to need roughly 5,500 to 7,000 running watts, staggered compressor starts, and disciplined load management.

Most importantly, size the generator using the air conditioner’s actual electrical requirements, the generator’s continuous output, your normal simultaneous loads, and the conditions where you camp—not the AC’s BTU rating alone.

Related Reading:

Best Quiet Inverter Generators in 2026

Best Quiet Inverter Generators for RV Camping

Best Lightweight Quiet Inverter Generators Under 50 Pounds

Best Quiet 2000–2500W Inverter Generators for Camping

Best Quiet 4500-Watt Inverter Generators for RV Air Conditioners

What Can a Honda EU3200i Run? RV and Home-Backup Wattage Guide