How Many Watts for RV: Air Conditioner and Appliances

Why RV loads are different from home loads

Sizing a generator for an RV is different from sizing one for a house, because the generator must feed the RV power panel through a single cord and cover whatever the rig draws while you are parked. The starting point is understanding the two figures on any generator: the running (continuous) watts it can hold for hours, and the starting (surge) watts it can deliver for a moment when a motor kicks on. The learn article on running watts vs starting watts explains the difference, and what generator watts mean covers how makers state the rating on the label.

For an RV, the practical approach is to add the running watts of everything you expect to run at the same time, then add the largest starting surge among those loads. That total is the minimum you should shop against. The most common mistake is sizing off the air conditioner's steady running figure and leaving no room for the compressor startup, which is what actually trips a small generator.

The air conditioner drives the sizing

The roof air conditioner is almost always the deciding load on an RV generator. When the compressor starts, it draws a brief surge that can be several times its steady running draw, because the motor has to overcome inertia before it reaches speed. The learn article on generator inrush current explains why motors behave this way. Size the unit so it can deliver that starting surge, not just the steady load, especially on hot days when the compressor cycles on and off repeatedly.

A soft start kit is a retrofit that lowers the starting surge of the AC compressor. It is worth considering for a smaller generator, because it can let a less powerful unit handle an air conditioner that would otherwise exceed its surge rating. If you install one, follow the maker's instructions and verify the reduced surge before relying on it.

Add up the appliances you run together

Build the load list from the rig's actual 120V appliances rather than guessing. Common loads include the converter and battery charger, the refrigerator in electric mode, a microwave, a coffee maker, a TV or laptop charger, and sometimes an electric water heater or space heater. The key is to note which ones you run at the same time; you rarely run the microwave while the water heater element is on, so you only need to sum the loads that actually overlap.

• Converter and battery charger: a steady draw whenever the RV is on generator power.
• Roof air conditioner: the largest single load, with a significant starting surge.
• Microwave and coffee maker: high draw for short bursts; count them individually.
• Refrigerator on electric mode: a motor load with a modest start.
• TVs, laptops, and phone chargers: small, but they add up across a weekend.
• Electric water heater and space heaters: high draw; avoid overlapping them with the AC.

Keep headroom and mind the cord

Use the higher of the running or starting figure for each item, add the overlaps, then keep a margin on top. The learn article on generator headroom explains why running at the edge of the rating is hard on the set, and cord gauge and length shows how a long run can drop voltage and starve the AC.

Placement and carbon monoxide are part of sizing

Sizing is only half the job. Portable generators produce carbon monoxide, and the CPSC warns that one generator can make as much CO as hundreds of cars. CO is colorless and odorless, and it can kill in minutes. Never run a generator inside the RV, in a garage, carport, or under a slide-out, and keep it away from any window, door, or vent where exhaust could blow back in. The CDC recommends operating the generator outdoors more than 20 feet from windows, doors, and vents, with the exhaust facing away.

Fit a battery-operated or battery-backup CO alarm inside the RV, on every level and outside sleeping areas, and test the batteries on a schedule. The EPA notes that deadly CO levels can build up quickly and can linger for hours even after the generator is shut off, so do not rely on a breeze or an open window. If you feel headache, dizziness, weakness, or nausea, get to fresh air immediately and call for help. See the generator safety checklist for the full set of placement rules.

Match the generator class to the rig

Once you know your surge target, match it to a generator class. A small inverter generator suits a camper with modest loads and no air conditioner. A mid-size portable in the 3,000 to 5,000 W range handles one roof AC plus the basics. Larger rigs with two air conditioners or electric heat move up to the 5,000 W-and-up classes. For quiet, stable power for laptops and other sensitive gear, an inverter model with lower total harmonic distortion is a better fit; see THD and sensitive electronics.

Compare current models in the RV-ready generators guide, the RV-ready inverter generators guide, and the 3000 to 5000 W guide. For larger rigs, the 5001 to 9000 W guide covers the heavy class. If you want propane as a fuel option, a dual-fuel model keeps your fuel supply flexible.

What to pick for your use

Questions

Can I run a generator inside my RV if I open a door or window?

No. The EPA and CPSC say never use a portable generator indoors, in a garage, or in an enclosed space; CO can reach deadly levels quickly and linger for hours after shutdown. Run it outside, far from the RV.

Do I size my RV generator by starting watts or running watts?

Use the starting surge figure for the largest motor, usually the air conditioner, plus the running watts of everything that runs at the same time. The running vs starting watts article shows how the two figures relate.

How far should the generator be from the RV?

The CDC recommends operating the generator outdoors more than 20 feet from windows, doors, and vents, with the exhaust facing away from the RV.

Does a CO alarm inside my RV let me run the generator closer?

No. An alarm warns you, but it does not make closer operation safe. Keep the generator far away and keep a battery-operated CO alarm on every level and outside sleeping areas.

Can I connect two small generators instead of buying one large one?

Yes. Many inverter models parallel to combine their output, which can be lighter to carry than one large unit. Check the parallel kit benefits article and compare the RV-ready inverter guides for compatible models.