How Big Of A Generator Do I Need To Run Central Air?

How Big Of A Generator Do I Need To Run Central Air

While central air conditioners are vital in hot weather, they also need a sustainable energy backup during power outages to keep the temperature cooler. To meet this purpose, choosing the right size of generator is so crucial.


A central air conditioner typically consumes between 3,500 and 4000 watts per hour. Hence, by perfectly calculating the starting and running wattage of your AC, you can find out which size of generator will work better.

So, calculating the need and the size of your generator is not very difficult. The following article will get you through everything you need to know before buying a generator to run your central air conditioner.

Let’s get started:

The Best Size of a Generator You Need To Run Central Air Conditioner: A Complete Guide

How Big Of A Generator Do I Need To Run Central Air

While a generator can work best as a power backup to your central air conditioner, choosing the right size of a generator is a matter of great concern too.

However, you can get an accurate backup supply only when you have properly determined the required power.

Let’s see how important it is for you to determine your need and figure out the perfect size of your generator:

Determine Your Need

Before you select a generator to power your central air conditioner, consider properly measuring the required backup.

Some generators are heavy and can power all the appliances at the same time, while other generators are particularly designed for facilitating your central air conditioners only.

By defining your need, you can go for the best option and can save your time and money too.

Figure Out The Right Size

Figuring out the right size of a generator is also important because it benefits the generator and your valuable appliances as well.

However, if the generator is too small, it won’t be able to provide enough power to your devices. On the other hand, if the generator is overutilized, it may prove very costly.

To make it simpler, if the size of your AC is 24000 BTU which is equal to 2 Ton, there is no need to buy a generator of more than 8 kW. Besides, if you want it to power the whole system, keep 12 or 18 kW generators at the top of your list.

2 Major Types Of Generators

How Big Of A Generator Do I Need To Run Central Air

The following are the two major types of generators:

Standby Generators

Standby generators are also known as backup generators. They have sufficient capacity to support a large system. Also, they can be bigger in size and are permanently installed in the open air.

Here are some key benefits of standby generators you should know:

  • Automatically turn on when there is an outage
  • Less noisy
  • They are safe and secure even in strong weather conditions
  • Power the whole system because they are directly attached to the main power supply point
  • Needs less maintenance

Portable Generators

Smaller in size, bigger in worth. Portable generators are lighter and easy to move. Plus, they can also bear an entire load of your AC to the maximum.

Here are some other advantages of portable generators you should know:

  • Can be taken to any location where there is a power outage
  • Easy to operate and super easy to maintain
  • No need to call the expert for installation

Which Type Of Generator is Best to Run a Central Air Conditioner?

As central air conditioners require more continuous power to work well, standby generators are fit for them. Unlike portable generators, they can facilitate both air conditioners and other appliances simultaneously.

To add more, where a portable generator can only power approx 12,000 watts, a standby generator has enough capacity to work for up to 60,000 watts which are best for central air conditioners.

Why Calculating The Right Size Of the Generator is Important?

Finding the accurate size of your generator is very important before you buy or even install it. Because it may prevent sudden shutdowns and interruptions in the power supply, it is necessary to know how much load you can put on it.

However, if both the capacity of the generator and the load are properly checked, you can prevent unusual breakdowns and can also enhance the overall performance of your generator.

So, How Do You Determine A Generator’s Size?

Always keep these two things in your consideration when figuring out the size of the generator:

  1. The wattage your AC unit consumes when running.
  2. The start-up wattage flow

You can check the accurate wattage of your AC from the specifications section. Once you’ve found the exact wattage of your AC, go through the list of generators and see which generator can fulfill the requirement.

In addition, you can also get the wattage size of your AC unit by calculating its tonnage size. Hence, by dividing the number of BTUs by 12000, you may get the AC unit’s tonnage capacity.

Size Table

Here is the table to figure out the amount of Watts according to the dimensions of the AC unit.

BTU Size

Tonnage Of AC Unit

Estimated Watts

kW (Kilowatt)


1 Ton

3800-4000 W

4 kW


2 Ton

7800-8000 W

8 kW


3 Ton

11800-12000 W

12 kW


5 Ton

17500-18000 W

18 kW

Benefits Of Calculating The Right Size

Following are some of the major advantages you can get by calculating the right size of your generator:

  • The generator provides you with an enhanced power supply
  • The lifespan of your generator may also increase
  • Uninterrupted power supply for longer operations
  • With a persistent supply of electricity, your expensive appliances remain safe from voltage fluctuation

Related: How to Connect Generator To House Without Transfer Switch?

Frequently Asked Questions

Is A 3.5 KVA Generator Enough to Run my Central Air Conditioner?

Although, you can use a 3.5 KVA generator to run your central air conditioner but ensure that no appliances other than the AC are connected to the generator.

Because generators with 3.5 KVA have less capacity and can power one thing at one time, overloading it may cause great damage to your devices.

Can I Run Central Air Conditioner on a 10,000 Watt Generator?

Your central air conditioner will be able to run continuously for prolonged periods of time with the help of a 10,000 Watt generator. However, good maintenance and regular look after of the generator can be worth it.

Related: Can Portable Solar Generator Run a House?

Did We Cover Everything?

To sum up, the capacity of the generator and the unit’s power consumption must be carefully considered when running a central air conditioning system. However, the size of the generator required to operate central air relies on a number of variables, including the AC’s beginning wattage and its size.

Hence, the air conditioner may be harmed or provide you with unsatisfactory performance if you select a generator that is too small.

To make sure the generator can manage the load and offer security during power outages, consulting a certified electrician is essential. uses affiliate links (No Additional Cost For You). As an Amazon Associate, I earn when you purchase Using My Affiliate Link. Learn more.


Hi, Welcome to; My name is Shahzad, and I know about generators because I grew up in a country where power outage is very common. I share Tips, How-To, News, and Reviews for the best generators or anything related to generators.

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