Dueling Central Air Conditioners

Dueling Central Air Conditioners

How to Manage Two Central Air Conditioners

Staying cool takes a lot of power. A central air conditioner can use up to 6,000 watts to stay running throughout the day and 4-6 times that wattage to start up.

Now double that, and you'll realize how much power you would need to power not one, but two central air conditioners during a blackout.

However, if you have a large family and a large home, you probably have little choice but to keep both air conditioners running on a hot summer day, power outage or not. We'll tell you how to pick the right generator to run those two air conditioner units.

The Power of A/C Shedding

Standby Generator with Central A/CMost modern automatic generator transfer switches come with built-in A/C shedding functionality. A/C shedding is the ability for a transfer switch to "shed" or turn off the air conditioner so other appliances can get power. 

A/C shedding is crucial to being able to power two air conditioners. Since the amount of power it takes to start just one A/C unit is so great, the generator wouldn't be able to start both at once. With A/C shedding, the transfer switch prevents both generators from trying to start at once. Instead, it starts them one at a time while also balancing other power needs in the home.

The following sequence of events is an example of how A/C shedding can manage power loads:

  1. No A/C units are running. Generator power is being used for other home appliances.
  2. A/C unit 1 starts up and causes a surge.
  3. A/C unit 2 wants to turn on, but the transfer switch pauses it because it detects an overload risk while A/C unit 1 is also starting up.
  4. A/C unit 1 finishes startup. The power intake drops and stabilizes.
  5. The transfer switch now detects enough power to turn on A/C unit 2 and does so.

If at any point during this process another home appliance, such as an electric water heater, needs to turn on but there is not enough power, A/C unit startup and operation will be delayed or turned off.

As you can see, short of buying an extremely large, whole-house generator, A/C shedding is critical to running two central air conditioners, along with other appliances in your home.

Choosing the Right Generator 

If you need to power two central air conditioners, use our chart below for help finding the right type of generator.

For example, if you need to power two 4-ton air conditioners, you will want a 16-kilowatt standby generator with A/C shedding. Without A/C shedding, it would only be able to start up one 4-ton air conditioner.

Always consult with your installing electrician to confirm your A/C starting loads.

Generator A-C Sizing Chart


Should you need additional help in finding the right standby generator, our experts are standing by at 1 (800) 800-3317 or contact us.


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Jared, the Generator Expert
Generator Expert
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