Can I run a window air conditioner on a portable generator?

Tuesday, June 19, 2018

Most portable generators can handle at least a 6,000 BTU air conditioner, which needs between 500 and 600 watts. But, because the compressor component needs a 50% to 100% additional surge of power to overcome inertia at start-up, a small window a/c needs about 900 to 1200 watts briefly each time the compressor kicks in to start a cooling cycle.

    Even a 1,000 watt rated output generator will be adequate. You just can’t plug in additional loads that, when added to the requirements of the air conditioner, will exceed the generator’s surge rating. It is sometimes called “maximum output” and can only be sustained briefly by a generator. 

    A rule-of-thumb is that window air conditioners require about 1 watt for every 10 BTU, but the exact rating is listed on the data plate on the side of the cabinet. Sometimes only the amperage is listed. Since volts times amps equals watts, multiply the amps shown times volts (either 120 volts, or 240 volts for units over about 14,000 BTU) to get the wattage rating.

    If you need to get a window air conditioner that will put the absolute minimum load on your generator, one good option is the Frigidaire 5,000 BTU model FFRA051151-1, which is rated at 450 watts, 11.1 EER, and has a “Low Voltage Startup” feature that reduces surge requirement at startup. You can expect this size unit to be adequate for a room up to 150 square feet, and we recommend closing the supply register (vent) and taping over  any return air register in the room you chose, to prevent loss of cool air through the central a/c ducts.

   Some generators list their surge rating in big numbers on the side of the generator, when the actual continuous output is much less. That data plate shown below was on a generator with a big “4000” on the side, but the continuous output is actually 3300 watts.

    Here’s listing of average wattage of appliances that will run on a small to mid-size portable generator for calculating your total load. Some small generators do not provide 240-volt electricity, so a major appliance that needs 240 volts (such as a window a/c larger than 14,000 BTU, central a/c, range, cloths dryer, and most water heaters) will not work. Also, running a small window a/c and refrigerator/freezer at the same time may not be possible on the smaller generators. 

    Also, see our blog posts Which trees are most likely to fall over on your house in a hurricane? and What is the best emergency back-up generator for the power outage after a storm? 

• • • • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to a collection of our blog posts about HURRICANE RESISTANCE:

Should I buy a house that has hurricane flood damage?

Should I buy a house with hurricane flood damage that has been repaired?

• What can I do right now to prepare my house for a hurricane? 

Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

How much hurricane wind speed can a mobile home survive?  

Can I do my own wind mitigation inspection?  

• What is the wind mitigation inspection for homeowner's insurance? 

What is the best emergency back-up generator for the power outage after a storm? 

What are the pros and cons of concrete block versus wood frame construction? 

Is a metal roof for a mobile home approved for HUD Wind Zone 3? 

Why do so many more sinkholes open up after a hurricane?  

    Visit our HEATING AND AIR CONDITIONING and HURRICANE RESISTANCE pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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