What Size Generator do you need for a Window AC?

generator for ac unit

Running a window air conditioner with a generator is not as simple as plugging it in and turning it on. As with most appliances, you should know how many watts you need to run the AC unit. 

Many factors determine what size generator you need for window AC. Some of these include the type of air conditioning unit you have, how often you run it, and where you live. In this article, we will look at each of these factors and figure out what size generator you need to run your window air conditioner.

We will also explain the various generators used to power window air conditioners. We will also compare generators based on price, power output, and efficiency.

Generator Types For Window AC

Generators come in many different sizes. Some are designed for large companies, while some are small generators explicitly made for homes or businesses. 

There are three different common generators to power your air conditioner, and they vary in terms of their wattage.

  • Inverter Generator: An Inverter generator converts AC power to DC power, enabling it to maintain a constant current flow for your window air conditioner.

  • Portable Generator: Portable generators are ideal for providing emergency backup power. they are usually used to power small appliances which is why they may be suitable for window air conditioners with low power requirements 

  • Standby Generator: A standby generator uses an automatic operating system to switch on automatically when it senses power loss. These generators usually have more power output and can power all types of window air conditioners. 

Why is it Important to Buy the Right Size Generator?

You need to know how much electricity you use before buying a generator. To understand what size generator you need for your window ac,  you should first consider the watt consumption of your window ac unit. Wattage is measured in watts (W). 

To calculate the wattage of an appliance, multiply the number of amps used by the voltage (V) of the supply. Or better still, check the buyer's manual for your unit's watt consumption.

The 12,000 BTU window air conditioner has a running wattage of 1700 watts and a starting wattage of 5,100. To work effectively, you will need a generator with an average of 6,800 watts. 

The generator's wattage should be equal to or greater than the wattage of the appliances you wish to operate. Additionally, to avoid any hiccups in performance, you should make sure your AC unit is the only large appliance running on your generator.

When The Wattage is too Low

A generator with a low wattage rating consumes more power than needed, resulting in overheating. Overloading can cause fire and explosions. If you don't have an emergency plan in place, you could lose everything.

When the Wattage is Too high

The opposite problem occurs when using a generator with a high wattage. Generators with a high wattage consume less power than needed, which results in overcharging, and you will simply be incurring additional fuel costs.

Do Window AC Units Use A Lot Of Electricity?

An average 10,000 BTU window AC unit uses less than half of the energy it would take to run a central unit for the same amount of time. But if you have more than one unit, it can quickly add up.

Window AC units are very effective in small spaces. But if you intend to cool larger and different areas at once, installing a central air conditioner is more cost-effective. If you're an energy-conscious homeowner, then a power consumption meter is an easy way to keep track of just how much energy your air conditioning units are using.

If you find that your air conditioner uses a lot of electricity, you should consider replacing it with a new energy-efficient carrier model. But before you go out and buy a new air conditioner, make sure you understand why your old one uses so much power.

How much Power Does a Typical Window Unit Wattage

The wattage of your window air conditioner is classified into two-watt settings ( starting wattage and running wattage). These wattage settings determine the size of your generator needed to run it. You can find the wattage of your air conditioner by looking inside the manual or contacting the manufacturer.

A typical window air conditioner has a starting wattage rating of 2200 watts. As the motor runs, the amperage decreases, and the wattage usually goes down to about 1500 watts. If you have a larger system, you may need a bigger generator. For example, a 10,000 BTU window air conditioner has a starting and running watt of 3000 and 1200, respectively. Only a generator with a maximum capacity of 4200 watts would handle such a unit. 

Generator Size for Window AC Unit

As we mentioned earlier, one of the most important considerations when installing a window air conditioner is how much power it will draw from your generator. From 5000 BTU to 14000 BTU, these air conditioners are available in a wide range of sizes.

Running wattage for a 5000 BTU air conditioner is approximately 450. Depending on the size of the space, an 8000 BTU air conditioner may use as little as 715 watts. 1250 watts is all that is needed for a 14000 BTU air conditioner.

With a 1000-watt generator, you can run a small to medium-sized window unit and be OK. You'll need at least a 2000-watt generator to power a large window unit. A larger generator can be a better option if you need to power many appliances at once.

Having more than one generator can be beneficial, so you should also think about doing that. In this way, you can keep everything running without having to put too much strain on a single generator. Generally, a 2000-watt generator is enough to power units up to 14000 BTU incapacity.


Generally, determining what size generator you need for a window ac unit will depend on many factors, such as the size of your home and the amount of cooling power you need. However, we recommend using a generator that produces at least 1,000 watts of electricity. This will ensure that you have enough energy to efficiently run your window air conditioner.

If you struggle to power your window AC unit with a generator, follow these suggestions and upgrade to a newer, more efficient size generator for your window ac unit.