Generator for RV Air Conditioner: Sizing and Start-Up

What an RV air conditioner needs from a generator

An RV air conditioner is a motor-driven appliance. When the compressor starts, it draws a brief surge of power, often called starting watts or surge watts, before settling to a lower steady draw, the running watts. A generator listing that names two watt figures is giving you both: the first is usually the starting figure, the second the running figure. For an air conditioner, the starting figure is the one that matters most, because the generator must be able to deliver that surge without bogging down or tripping its overload protection.

The running watts are what the air conditioner uses once the compressor is up to speed. If a generator only meets the running figure but not the starting figure, the air conditioner may not start at all, or the generator may struggle and shut off. Read the watt figures on the listing carefully, and compare them to the air conditioner's requirements as stated by the RV maker. This article explains the terms; the exact numbers for your rig come from the RV's manual and the generator's listing.

Reading starting and running watts on a listing

Generator listings often show two numbers, such as "5,000 starting watts, 4,000 running watts." The starting figure is the maximum the generator can produce for a short moment, and the running figure is what it can sustain. For an RV air conditioner, you want the starting figure to be at least as high as the air conditioner's surge draw. The running figure should cover the air conditioner's steady draw plus anything else you plan to run at the same time, like lights or a refrigerator.

Some listings only state one figure. When that happens, the listing may not tell you whether it is starting or running watts. In that case, check the maker's page for the full specification. The site's guides compare generators on stated details, so the watt figures in each guide come from the listings. For a deeper explanation of the two figures, see Running vs Starting Watts.

Surge power and soft-start options

Surge power is the brief spike of electricity an air conditioner's compressor draws when it starts. It can be several times the running watts, but it lasts only a second or two. A generator that cannot supply that surge will not start the air conditioner. A soft-start device, sometimes called a hard-start kit, is an aftermarket component that reduces the surge by ramping up the compressor more gradually. This can allow a smaller generator to start the same air conditioner.

Soft-start devices are sold separately and are installed by the RV owner or a technician. The generator listing will not tell you whether a soft-start is included; it is a separate purchase. If you are considering a soft-start, ask the RV maker or the soft-start manufacturer whether it is compatible with your air conditioner model. The generator itself does not need any modification; the soft-start works on the air conditioner side. For more on surge power as a listing term, see Surge Power in Generators.

Sizing for your rig: what to check

To size a generator for your RV air conditioner, start with the air conditioner's specifications. The RV maker or the air conditioner's nameplate will list the running watts and the starting watts, or sometimes the amps and volts, which you can convert to watts. The generator's starting watts must meet or exceed the air conditioner's starting watts, and the generator's running watts must cover the air conditioner's running watts plus any other loads you expect to run at the same time.

The site's guides group generators by watt range, such as Best 3000 to 5000 Watt Generators and Best 5001 to 9000 Watt Generators 2026. Within each group, the listings state the starting and running watts. Compare those figures to your air conditioner's requirements. If you are unsure about the electrical load, an electrician or the RV maker can help you calculate it. This site does not size a home or an RV; the numbers come from the listings and the maker's pages.

Fuel and generator type for RV air conditioning

The fuel type does not change how the air conditioner draws power, but it affects how you refuel and how the generator runs. Gasoline is the most common fuel for portable generators, and dual fuel and tri fuel models also accept propane or natural gas. For an RV, a dual fuel generator lets you carry propane as an alternative to gasoline. The fuel choice is a shopping question about availability and your own preferences, not about the air conditioner's power needs.

Inverter generators are a popular choice for RVs because they are often lighter and more compact than open-frame models, but the type does not change the wattage requirements. An inverter generator with enough starting watts will start an air conditioner just as an open-frame model will. The site's Best Inverter Generator in 2026 and Best Camping Generators 2026 guides compare inverter models by stated details. For a full list of RV-friendly generators, see Best Generator for RV (2026).

Safety and carbon monoxide

Portable generators produce carbon monoxide, an odorless, colorless gas that can be deadly. Never run a generator inside an RV, a garage, a basement, a crawl space, a porch, or a camper, even with doors or windows open. Follow the maker's manual for placement, and read the carbon monoxide guidance from the CPSC and CDC. The site's safety articles point to those sources; this article does not restate their advice.

What to pick for your situation

Questions

What is the difference between starting watts and running watts for an RV air conditioner?

Starting watts, also called surge watts, are the brief spike of power the air conditioner's compressor draws when it starts. Running watts are the steady power it uses once running. The generator's starting watts must be at least as high as the air conditioner's starting watts, and the running watts must cover the steady draw.

Can a soft-start device let me use a smaller generator?

Yes, a soft-start device reduces the surge power an air conditioner draws at start-up, which can allow a generator with lower starting watts to handle the same air conditioner. The soft-start is installed on the air conditioner, not the generator, and you should check compatibility with the RV maker or the soft-start manufacturer.

How do I know what wattage my RV air conditioner needs?

Check the air conditioner's nameplate or the RV owner's manual for the running watts and starting watts, or the amps and volts. Compare those figures to the starting and running watts stated on the generator listing. If you are unsure, ask the RV maker or an electrician.

Is an inverter generator better for an RV air conditioner?

Inverter generators are often lighter and more compact, which can be convenient for RV use, but the type does not change the wattage requirement. Any generator, inverter or open-frame, must have enough starting watts to start the air conditioner. Compare the stated watt figures on the listing.

Can I run an RV air conditioner with a generator that only lists one watt figure?

If a listing shows only one watt figure, it may not tell you whether it is starting or running watts. Check the maker's page for the full specification. Without knowing the starting watts, you cannot be sure the generator will start the air conditioner.

Where should I place the generator when running an RV air conditioner?

Never run a generator inside an RV, garage, basement, crawl space, porch, or camper. Follow the maker's manual for placement, and read the carbon monoxide safety guidance from the CPSC and CDC. The generator must be outside, away from any openings.