What Generator Size To Run an Air Conditioner?

The typical households experience power outages on some occasions and for some period.

But, blackouts triggered by severe weather may go on for many days or weeks.

And, whenever this happens you still want your AC to be working and keeping you cool and comfortable.

And it makes you wonder what generator size to run an air conditioner? 

Typically it would take at least a 7,500 Watt Generator to power an 1.5 ton air con unit but the bigger and heavier the aircon unit the more power you need generator, a 3 ton would need arpound 14,000 watts and 5 ton up to 20,000 Watts.

Also in this article well show you how to go about selecting the model suited to your needs.

In this article we’ll review the best generators for air conditioners, discuss generator sizing, and power needs.

Let’s dive in…

3 Best Generators to Run an Air Conditioner

Champion 4000 vs Westinghouse WGen9500 vs DuroMax XP13000EH Comparison

Champion Power Equipment 100302 4000-Watt RV Ready Open Frame Inverter, Yellow
Starting Watts
Running Watts
Powered By
Duel Fuel
Engine Type
Noise Output (dBA)
CARB Compliant
Fuel Capacity
Run Time
Warranty Length

Champion 4000 Watt Inverter Generator


  • 4,000 Starting watts, 3,500 Running watts


  • Gasoline: Up to 17 hour run time at 25% load


  • Wireless remote start up
  • Moderately powerful 224cc engine
  • Quick Touch panel allows for easy access to controls including economy mode for better fuel efficiency
  • 120V 30A RV (TT-30R), two 120V 20A household outlets (5-20R) and a 12V DC automotive-style outlet with a dual USB adapter and battery-charging cables
  • OPTIONAL– Parallel Kit with included standard 50-amp RV outlet- allows you to increase power output by connecting up to two 2800+ watt inverters or digital hybrids


  • 2.9 Gallon gasoline tank


  • Dimensions (inches): 23.5×24.8×20.5
  • Weight: 97 lb
  • Wheel kit included


  • 64 dB


  • Low oil shutoff
  • 3 year limited warranty+ lifetime access to free technical support
  • CARB Compliant

Champion 4000 Watt Inverter Generator PROS

  • Affordable– Less expensive than the other options discussed
  • Quiet– At 64 dB, the Champion 4000 is quieter than many other options.
  • Portability– Lightweight and included wheel kit make this one of the more portable options

Champion 4000 Watt Inverter Generator CONS

Not as powerful as other options. This can not be used as a true home backup generator. Only to power a few things at a time.

Westinghouse WGen9500DF

The Westinghouse brand is known to produce high-quality generators and the Westinghouse WGen9500DF has been called the best out there by some owners. Let’s review the details, advantages and disadvantages.


  • 12,500 Starting watts, 9,500 Running watts


  • Gasoline: 12 hour run time at 25% load
  • Propane: 7 hour run time on 20 lb Propane tank


  • 457cc OHV engine
  • Remote Electric start
  • Two GFCI 120V 5–20R Standard Household Receptacle, One Transfer Switch Ready 120V L14-30R, and One RV Ready 120/240V 14–50R; All Outlets Have Rubber Covers for Added Safety


  • Dual fuel generator: Runs on Gasoline or Liquid petroleum gas
  • 6.6 Gallon fuel tank


  • Dimensions (inches): 27x26x26.5
  • Weight: 211 lbs
  • Wheel kit included


  • 74 dB


  • Automatic low oil shutdown
  • 1-3 year limited warranty
  • 25 foot extension cord helps get the generator out away from potential dangers (unless someone trips over the cord, of course)

Westinghouse WGen9500DF PROS

  • Powerful– Great power output with 9,500 running Watts is enough to be a true home standby generator and power major household appliances

Westinghouse WGen9500DFCONS

  • Noisy (74dB)
  • Heavy (211 lbs)

DuroMax XP13000EH

The DuroMax XP13000EH is top of mind when it comes to high-performing generators. This generator has enough power to be a true backup home generator and other major benefits as well as a few drawbacks.


  • 13,000 Starting watts, 10,500 Running watts


  • Gasoline: 10.4 hour run time at 50% load
  • Propane: 8.6 hour run time at 50% load


  • Powerful 500cc OHV 2 stroke engine
  • One 120/240V 50A heavy duty outlet, 1 120/240V 30A twist lock outlet, 1 120V 30A twist lock outlet, and 2 120V 20A household outlets


  • Dual fuel generator: Runs on Gasoline or Propane
  • 8.3 Gallon fuel tank


  • Dimensions (inches): 30x29x26
  • Weight: 234 lbs


  • 74 dB


  • Surge Arrest technology prevents generator from power surges
  • 3 year limited warranty on new generators/ 90 day warranty on certified refurbished generators
  • EPA approved
  • CARB Compliant

DuroMax XP13000EH PROS

  • Powerful– Great power output with 10,000 running Watts is enough to be a true home standby generator and power major household appliances
  • Durability- DuroMax XP13000EH is durable enough to last for many years
  • Safety– CARB and EPA approval means this generator is safer for you and the environment compared to other models. Surge Arrest is a helpful technology is preventing potentially dangerous power surges.

DuroMax XP13000EH CONS

  • Noisy
  • Heavy and bulky
  • Rust- This generator can rust years into ownership

Durostar DS10000E

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The DuroStar DS10000E is another generator on our list with more than ample power to support air conditioners as wel

l as some other household appliances or outdoor activities.

  • 10,000 Starting watts, 8,000 Running watts


  • Gasoline: 10.4 hour run time at 50% load
  • Propane: 8.6 hour run time


  • 439cc OHV 4 Stroke engine
  • Power Panel with (2) 120V household GFCI outlets, (1) 120V 30A twist-lock outlet, (1) 240V 30A outlet, and (1) 240V 50A outlet. The panel also includes a voltmeter and 12V DC charging posts for charging external batteries


  • Dual fuel generator: Runs on Gasoline or Liquid petroleum gas
  • 8.3 Gallon fuel tank


  • Dimensions (inches): 40x29x27.5
  • Weight: 220 lb
  • Wheel kit included


  • 72 dB- Idle control help reduce noise


  • Surge Arrest technology prevent generator from power surges
  • EPA Certified
  • CARB Compliant
  • Approved in 50 states

Durostar DS10000E PROS

  • Powerful– Solid power output with 8,000 running Watts is enough to be a true home standby generator and power major household appliances as well as outdoor work or recreational needs
  • Eco Friendly

Durostar DS10000E CONS

  • Heavy
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How To Tell the Size of Generator Needed To Run Air Con

The truth is, it is tiring to remain stuck without an AC in the course of extended blackouts.

If you are, then you need to look for a standby generator to provide power in a future failure.

Do you experience power loss during hot weather?

Then you’ll need to have essential things like the air conditioner running. For you to be safe on your generator selection, then you need to:

1) Know the Available Generator Types: You have to know that the market offers two categories of generators. The ones you can move from one point to another are portable generator units and standby types that you must install outdoors while connected to the power line.

Portable generators are the most popular because they are smaller and lighter. They are also cheaper and more convenient to use, but stationary or standby generators are a good alternative if you’re a heavy user of electricity.

As expected, both have benefits and drawbacks which can help you decide as well.

Despite the fact that a portable generator can operate continuously for up to 10-20 hours (depending on the generator model),

For you to avoid frustrations, the stationary or standby one is the best choice as a whole house generator.. With this, you will experience:

-The added power since the biggest portable generator has only 12,000 watts. The machine will not push its wattage limit even when large central ac units are working. Most smaller portable generator units are ruled out by this consideration alone.

-There is less maintenance needed, unlike the portable generators. Since the energy consumption never gets exceeded, you will be spending moderate resources. For instance, you refuel once in a while and have little time in maintenance.

2)  Understand How The Generators Get Sized

The current progress of technology in the engineering industry has gone to generators too. The units come in different sizes.

Many individuals think the term size refers to the physical dimensions, but instead, it denotes power output. The extent of the measurements comes in capacities of power like W, watts or kW, kilowatts.

But, does the generator scope matter? Yes, if you overwork the equipment, it can either shut down or overheat. In turn, the associated risks can spoil the generator and other household appliances. Also, if you buy a potent generator beyond your needs, it means you will be overpaying.

The unit and running costs can force you to break the piggy bank. Well, there is no harm in having an expert electrician help with the inspection. You can read more about generator sizing here.

Yes, a 12,000 watt generator will produce more than enough power to run a central air. A large, 3 ton central air conditioner needs at least 7,200 starting Watts and 5,400 running Watts to operate, so 12,000 Watts is plenty.

Will A 10000 Watt Generator Run Central Air?

Yes, a 10,000 watt generator will produce more than enough power to run a central air. A large, 3 ton central air conditioner needs at least 7,200 starting Watts and 5,400 running Watts to operate, so 10,000 Watts is plenty.

Will A 9500 Watt Generator Run Central Air?

Yes, a 9,500 watt generator will produce more than enough power to run a central air. A large, 3 ton central air conditioner needs at least 7,200 starting Watts and 5,400 running Watts to operate, so 9,500 Watts is sufficient.

Can A Whole House Generator Run Air Conditioner?

Yes, a whole house generator can run an air conditioner as long as the generator provides more than 7,200 starting Watts and 5,400 running Watts for a 3 ton ac unit or larger.

The smallest generator to run air conditioner needs to have at least 2,800 Starting Watts and 1,800 running Watts.

How To Get The Power Details For Your Equipment?

Usually, the information is available in the documentation plate or owner’s guide in the purchaser’s kit of your device. Find out the running and starting required by every appliance. In some cases, both are the same, but where necessary, obtaining the peak wattage is vital.

You need this because if your devices consume added power during surging than what the generator produces, you will not manage to run your machines.

An alternative way to solve the problem of what size generator to run an air conditioner is by totaling the wattage of all you need to stay on during blackouts.

Before bringing in the calculator, remember that some machines draw extra wattage for a moment while running. The surge watts can interfere with the calculations if not included.


What’s The Average Air Conditioner Wattage?

A 13K BTU Window air conditioner units need at least 2,800 starting Watts and at least 1,800 running Watts while the larger 3 ton central air conditioners need at least 7,200 starting Watts and 5,400 running Watts.

Consider The Outside Temperature

When temperature and humidity increase outside, the power needed to start your ac unit increases, and the generator’s output decreases.

Unluckily, that means when you will require high power to get your ac unit operating. The generator will, in turn, be producing a low energy rating because of the high temperature.

The input of every air conditioner is steady and usually measured to be 35C outdoors and 27C indoors with 50% humidity.

An increase in temperature raises the electrical energy necessity of the device. You can choose a popular generator size that is trendy for dimensions and fuel efficiency.

Considering aspects like temperatures that often affect the device’s working, some models will suit a central ac unit

– Lower likelihood of asset destruction

Where Should You Buy Your Generator?

Not only will you be buying a vital company or home asset but also an appliance you will depend on for primary or backup electrical power in the future. The time may be during a disaster, so determining where you need to get a good deal is a fundamental concern not worth overlooking. Some of the factors that play a role in where to close the generator deal include:

– Years of operational experience

– Provide full-service when needed

– Certification of the technicians

– High-quality equipment and installation machines

– Supportive and knowledgeable support or office staff

– Tested products before deliveries

– Competitive prices and quotes always

Regularly Maintaining Your Generator

By now, you know that the right size of generators is a great way to cut your energy bills and keep all your appliances powered efficiently.

However, To keep your generator in good working order, you need to keep it cleaned and well-maintained.

It’s essential to make sure your generator is always in good condition, or you can end up with an expensive breakdown or having to replace it.

Here are some easy maintenance tips that will keep your generator running at its peak performance for years to come.

-Regularly check the oil

-Keep all of the moving parts lubricated

-Clean any areas of your generator that are caked with dust

-Change the spark plugs

-Clean the air filter

-Store it in a safe place

So, Which Is Best Size Generator To Run Air Con?

All the above mentioned generators have more than enough power to run an air conditioners.. So the best option depends on personal preferences, but let’s dive into which generator is best for each area.


The best performing generator out of the bunch is the Westinghouse Wgen9500DF. This dual fuel generator gets up to 12 hours of run time on gasoline and at 9,5000 running watts is powerful enough to be a true standby home generator.


Although the Champion 4000 Watt Generator is the least powerful of the options discussed.


The Champion 4000 Watt Generator is the lightest by far at only 97 lbs. It’s also relatively compact and comes with a wheel kit for added mobility. The Champion is the most portable option.



The safest option is the DuroMax XP13000EH model. This one is CARB compliant, EPA Approved.. and approved in all 50 states (Including California). Its Surge Arrest technology also prevents the generator from power surges.


The Champion 4000 Watt Generator is the quietest at only 64 dB. However, this is still not super quiet. There are other generators with noise levels in the 50s and even no noise solar generators to consider if noise is a big buying factor for you

  1. Champion 4000 Watt Inverter Generator 
  2. Westinghouse WGen9500DF
  3. DuroMax XP13000EH Portable Generator
  4. Durostar DS10000E Portable Generator

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Last update on 2023-01-01 / Affiliate links / Images from Amazon Product Advertising API