Can Generators Power an Air Conditioner?

Hello folks and welcome to! Today we will be taking a look at what it takes to run your air conditioner during a power loss event. To me, losing power during the summer is the worst. At least in the winter months you can start a fire. You can put your frozen food outside in the snow. You’re not uncomfortable and food isn’t going to waste. However, in the summer it is a completely different story.

I live a hundred miles or so outside of Kansas City out in the boonies. Power loss can happen quite a bit out here. When it does it’s either from winter blizzards or from severe summer storms. (We are in Tornado Alley after all.) Kansas summers can be quite brutal. As I write this article it is August and today’s high is one-hundred and one with high humidity. A power loss today would not be optimal. The house would warm up in only a few hours.

Having a generator on hand and ready to go can solve this problem. That being said, powering your air conditioner with a generator is a lot more complicated then powering your computer or lights. Air conditioners require a lot of power to run and if you’re not careful you can end up purchasing a generator that simply doesn’t have the capacity to handle an air conditioner.

Starting Watts, Running Watts, & Transfer Switches

Before I get into the various types of air conditioners out there I first want to make sure you understand some variables. There is a lot of math involved with generators. When working with them it is important to know the amount of starting watts and running watts of the appliance you are attempting to power. Not all things you’re looking to power have starting watts, but the ones that do you need to add them in your calculation.

Starting watts are just that. It is a measurement of the amount of power to start an appliance. In many cases a larger appliance will have a significantly higher amount of starting watts when turned on. An example of this would be a refrigerator, or an air conditioner. Both of these appliances have refrigeration cycles to produce a cold environment. A key component in this refrigeration cycle is the air conditioning compressor. The compressor requires an initial surge of power to kick it on. But, once it has been turned on the amount of power it needs lessens.

This is why it is critical to include starting watts in your calculations. If you glanced at your air conditioner and saw it only needed ten-thousand running watts but neglected to check the starting watts then you could end up buying the wrong sized generator. Again, it is always best to overestimate the generator size then under.

Another point I want to make in this section is the concept of a manual transfer switch. There are many different types of air conditioners out there. You could be facing a completely different setup depending on your air conditioner. A good example of this would be a window air conditioner versus a central air system. As you know, a window air conditioner simply plugs into your standard wall socket. In the event of a power loss it can be plugged into your generator via extension cord. Nothing changes here.

A central air system is different. The central air conditioner is connected directly to your circuit box. In most cases it has its own circuit switch. There is NOT a way for you to simply plug this air conditioner into your generator. This is where a manual transfer switch will come in handy. The concept here is that when your power goes out you can go to your circuit box and switch off the power from the city and switch over to your alternative generator power source. This allows you to power EVERYTHING on your circuit box.

The downside of these transfer switches is that they have to be installed and configured. I do not have the knowledge to do this and I am assuming most of you do not either. To be absolutely safe it is best to hire an electrician to do this install for you. The good news is that once it is done then you have one less thing to worry about during a power loss event.

Types of Air Conditioners

Alright so now we can get into the meat and potatoes of this article. I’ll be the first to tell you that air conditioners and everything that goes with them is a passion of mine. Yes, I know, it is a strange passion to have. It all stems from another website that I created known as . The site is completely dedicated to air conditioners and refrigerants. So, I consider myself a bit of an expert on the various types of air conditioners.

Now the question posed at the top of this article is can my generator run an air conditioner? To answer that we have to determine exactly what type of air conditioner we are dealing with. Is it a central air? Is it a mini-split? Portable? Window? Each one of these applications can impact my answer.

Central Air Conditioners

Most homes or apartments nowadays come with central air conditioners. Well, this holds true in my neck of the woods in the Midwest. I know in certain parts of the country central air systems are the exception. My brother, for example, lives in Seattle and they had to go out and buy a window unit the other day as their home has no central system. It got him through in a pinch. Personally, I’ve always been a fan of central air systems. They are efficient, clean, and neat.

That being said… when it comes to alternative power there is a big downside to central systems. A central air conditioner consumes and requires a lot of power. They also come with a significant amount of starting watts just to get the machine up and running. Most residential central air conditioner systems range between one to five ton. Ton is a measurement of the cooling capacity of the air conditioner. You may also see these measured in BTUs. Just for your reference, one ton equals twelve-thousand BTUs. A standard sized home is going to be using either a three ton or four ton central system. Some of the larger homes out there may use a five ton or may end up having two three or four ton units installed.

What does all this mean when it comes to powering with your generator? Well folks, you are going to be hard pressed finding a portable generator that can power a central air system. In fact, as a rule of thumb if you have a central air system that needs powered then you should be looking at a standby generator rather then a portable. Standby generators are a permanently installed unit on the outside of your home that will turn on automatically in the event of a power loss. They are MUCH bigger and can produce a lot more power. In many cases folks will route these directly to their propane tank.

I mentioned before that I live out in the boonies, well like most folks out here we have a propane tank that we use for heating, cooking, and water heating. It is an eight-hundred gallon tank that we would fill up once a year. A standby generator can be tied directly into this propane tank or you could also opt for getting the generator its own separate propane tank. My parents did this with theirs and they rarely have to fill it up at all.

The reason I push for a standby generator when it comes to central air conditioners is that you are going to be hard pressed finding a portable generator that has enough power to run your central air system. Let’s look at some numbers to illustrate the point here. A three ton air conditioner will need a minimum of thirteen-thousand watts to run. A four ton unit will need seventeen-thousand, and a five ton unit will need twenty-thousand watts.

The closest portable generator I could find on this topic was this twelve-thousand watt unit from Westinghouse. It is a massive portable generator that can produce a lot of power… but you’ll notice that we are still one-thousand watts shy of the three ton thirteen-thousand watt requirement. You’ll also notice the price on this. It’s over two-thousand dollars. That is a huge investment and frankly, if it was me, I’d rather invest in a full standby system and know that it is setup and ready to go. You’ll also get the reassurance that you will have enough power to run everything in your home. Also, if you’re going to be spending that kind of money on a generator it might as well be a standby.

If you have your heart set on a portable system though then you can look around for larger units. You may even look at your central air conditioner to find the precise starting/running watts. All I can say is do not hold your breath. Chances are you’ll need to go with a standby system. Or, you can look purchasing a window or portable air conditioner as an alternative solution. We’ll get into these in our next section.

Window/Portable Air Conditioners

I feel like over the years the window air conditioning unit has gotten a bad wrap. I’m not really sure where it comes from but there appears to be a certain stigma attached to them. Some say they don’t look good or they lower the quality of the house. Whatever the reason is, the thinking exists. I have to say that I do NOT agree with this at all. Window air conditioners are a lifesaver and can give even the poorest person a way to get nice cool air. You can find a bare bone window unit for under two-hundred dollars. (Example being this Amazon Basics one). The install on a window unit doesn’t take much time at all either. On the smaller units you don’t even need brackets installed.

I also like to link portable air conditioners in with the window units. They are both great appliances that provide cool air at a low price point. Portable units have an even easier install. Just route the tube to a nearby window, put up the frame, and there you go. You have cool air now. I had mentioned in the central air section that these air conditioners are a great substitute for when your central air is down. It will save you from having to buy a large standby generator or a very large portable generator.

Now, just like with central systems, window/portable air conditioners come in different sizes. You’ll notice that these aren’t measured in tons but instead of BTUs. This is because in most cases portable/window units do not exceed the twelve-thousand BTU threshold to equal one ton. An entry level window/portable air conditioner is going to come in at around five-thousand BTUs. These types of air conditioners will have a surging wattage at around fifteen-hundred and a standard running watt range of about one-thousand.  These five-thousand BTU units are a great solution for air conditioning during a power loss or even during an RV or camping trip. At most you are using fifteen-hundred watts.  If you have a four or five-thousand watt generator then you have plenty of extra wattage to cover other areas such as lighting, computers, or a refrigerator or freezer.

On the other hand, if you have a ten-thousand BTU air conditioner you are working with then the required wattage is going to be significantly higher. As you would expect, it is about double at around twenty-five hundred starting watts and around two-thousand running watts. Note that the above values are estimates based on air conditioner BTUs. Each air conditioner is different and it is always best practice to check the air conditioner owner’s manual to find the exact electrical information. This will ensure that you know what you’re getting into.

Mini Split Air Conditioners

The last mainstream air conditioner to mention are what’s known as the ductless mini-splits. I love these types of air conditioners as they provide air conditioning to homes that do not have duct work. Yes, the portable/window air conditioners do this as well, but a mini-split system offers far more power then these other portable air conditioners. It also allows you to have various zones throughout the home whereas a portable only provides cold air in one specific area.

Mini split systems are the in between a portable unit and a central duct system. Because of this you will notice the BTUs and the power required to run mini splits can be quite high… but not quite as high as a central air system. These ductless systems typically come in a one ton, one and a half ton, two ton, and three ton sizes. If you recall in our central air conditioner section we stated that a three ton unit is typically what most homes use. Since the ductless systems start with a one ton size you should be able to get away with a portable generator with these appliances, but again remember that it is a case by case basis.


Well folks, I do have to apologize for the length of this article. I can get a bit carrier away with topics like these, but I do hope that I was able to provide you with the answers that you were looking for. Like so many things there is no easy answer… instead many factors have to be considered. Lastly, please note that this article is intended for informational purposes only. We here at ToughAssTools are not liable for any property damage or personal injuries that can occur when operating generators.

Thanks for reading,

Alec Johnson


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