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What Size Generator To Run 4 Ton AC Unit? (Ultimate Guide)

Edited ByMark Allen Hours Updated onJanuary 15, 2024 Categories Generator

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  • What Size Generator Do I Want To Run A 4 Ton AC Unit?
  • Understanding Generator Capacity and AC Requirements
  • What Types Of Generator Do I Need For A 40 Ton AC Unit?
  • What To Look For When Buying The Best Size Generator For A 4-Ton AC Unit?
  • FAQs About The Right Size Generator For a 4-Ton AC Unit
  • The Bottom Lines

Generators are assessed according to the various amount of electrical power such as KW. 

Most of the time, AC holds more power than any other appliance in your home or office. So you need an appropriate generator to power your AC.

And if you have a 4-ton AC unit then this article is for you. Just take a look that what size generator you need to run a 4-ton AC unit.

What Size Generator Do I Want To Run A 4 Ton Ac Unit

Click Here To Check Recommended Generators

What Size Generator Do I Want To Run A 4 Ton AC Unit?

To run a 4 Ton AC unit, you typically need a generator with a capacity of at least 20,000 to 25,000 starting watts. Once running, the AC will require around 15,000 continuous watts. A generator that can produce at least 20-25% more power than the running wattage is recommended.

Chart of generator sizes for a 4-ton AC unit:

Wattage of 4-ton AC unit (W)Minimum generator size (W)
40004800
45005400
50006000
55006600
60007200

Recommended generator brand to run 4 ton ac unit:

  • WEN DF450i Super Quiet 4500-Watt Dual RV-Ready Portable Inverter Generator
    WEN DF450i Super Quiet 4500-Watt Dual RV-Ready Portable Inverter Generator with Fuel Shut-Off
    • Dual fuel design runs on both gasoline (4500 surge watts, 3500 rated watts) and propane (4500 surge watts, 3150 rated watts)
    • Auto Fuel Selection Technology automatically switches from propane to gasoline for longer run times
    • EPA III and CARB compliant
    logo Amazon Amazon
  1. DuroMax Dual Fuel Portable Generator- Gas or Propane Powered
  2. Champion Power Equipment Portable Generator

Understanding Generator Capacity and AC Requirements

Wattage vs. Running Watts

Every AC unit needs power to start. This is called wattage. Once it’s running, it uses running watts. Sometimes, at the start, an AC needs more power. We call this surge power. Surge power is short. It’s only a few seconds. But it’s important. Generators must handle this without trouble. If not, they might shut down. Or they won’t start at all. So, always check the surge wattage of your generator. Make sure it’s more than your AC’s wattage. For safety, never use a generator that gives more power than your house can handle.

Starting Watts for AC Units

AC units need more power to start. This power is starting watts. Different things change the starting watts. The kind of AC you have matters.

So does the weather. Even the AC’s age can change things. If your AC is old or it’s very hot outside, it might need more power.

You can check this with a tool called a wattmeter. Or you can use math to guess the right amount.

You can also estimate the starting watts for your AC unit by using a formula. The formula is:

Starting watts = Running watts × Multiplier

The multiplier is a number that depends on the type of your AC unit. Here are some common values for different types of AC units:

Type of AC unitMultiplier
Window3
Portable3
Split4
Central4

For example, if you have a window AC unit that has a running watts of 2500 W, you can estimate the starting watts by using the formula:

Starting watts= 2500 × 3= 7500 W

Continuous Power Needs

How long do you use your AC? If you use it all day, it needs more power. If only for a few hours, it needs less. This is called continuous power.

Keeping your AC clean helps too. Clean ACs use less power. So always clean the filters. To know how much power your AC uses all the time, use a wattmeter.

Or again, you can guess using some math.

For example, if you have a window AC unit that has a running watt of 2500 W, you can use a wattmeter to measure the power when your AC unit runs continuously for an hour or more.

You can use the same formula as before, but with a different multiplier:

Continuous power needs = Running watts × Multiplier

Here are some common values for different types of AC units:

Type of AC unitMultiplier
Window1.5
Portable1.5
Split2
Central2

For example, if you have a window AC unit that has a running watts of 2500 W, you can estimate the continuous power needs by using the formula:

Continuous power needs = 2500 × 1.5 = 3750 W

What Types Of Generator Do I Need For A 40 Ton AC Unit?

Though there are three types of generators available, an Inverter generator is best for AC.

But nowadays Standby generators becomes more popular for their latest technology. Let’s see how they differ from each other.

Portable Generator

A portable generator is run on gas or fuel. In case of power loss, your portable generator can provide emergency power backup.

Some portable generator comes up with CO-reduced technology.

It is best for powering small appliances but if you want to run a central AC then you will need a large watt portable generator.

What generator size for camper?

Inverter Generator

Inverter Generator

An Inverter generator powered by an engine converts the AC power into DC power. It keeps a constant circulation of current to an appliance.

And that is how it is an ultimate option for AC units. It is also the quietest generator of the others.

Standby Generator

A standby generator comes with an automatic operating system which is totally an electrical system.

It automatically runs when there is an emergency power loss. It has an automatic power switch that senses power loss. 

An easy and automatic generator like a standby generator might be anyone’s first choice.

>> What size generator to power 5 ton ac?

What To Look For When Buying The Best Size Generator For A 4-Ton AC Unit?

What To Look For When Buying The Best Size Generator For A 4-Ton AC Unit

Buying a generator is not an easy thing. There are many things to look for.

Power

All you need to know about is the maximum and rated power which refers output system of a generator. 

When maximum power refers to output that can last up to 30 minutes, rated power goes through for a long period of time.

That is why rated power is more important than maximum power.

>> What generator size to run 5hp air compressor?

Performance

Generator Performance

Know how much your generator handles a load of your AC unit when a sudden spike in voltage hits.

And also see how long it runs and how easy it runs while emergency power backup is needed.

You must know the engine’s quality before buying a generator for your AC as well as its functions. 

Back up 

You would like to choose such a generator which automatically starts when there is a necessity for power back up.

A standby generator functions like that. It has an automatic switching system.

There are also such types of generators available that you have to start on your own. In this modern world, you will surely go for the automatic one.

Safety

Generator Safety

Nowadays producing CO poisoning is a big issue for the world in case of global warming.

There are many new features that come to the market which reduce the risk of  CO poisoning.

Many portable generators also come with these new features. Before buying make sure how much your generator reduces or prevents CO. 

Noise Level

Generators usually produce loud sounds. Large generators produce more noise than smaller ones.

An inverter generator, sizing 14-20 KW might produce roughly more noise than any other generator.

There are some new features of generators that come to market which produce lower noise.

FAQs About The Right Size Generator For a 4-Ton AC Unit

How Long Does A Generator Run For A 4-Ton AC Unit?

There is no specification about this issue. Most of the generators can run for 24 hours while some can 48-72 hours.

How can I reduce noise from the generator?

Locate the generator unit away from living areas. Install a protective enclosure to dampen operating noise.

Should I get a generator that can also power other appliances?

Yes, as long as critical household circuits don’t exceed the generator’s rated wattage, you can power additional lights and appliances.

How often should I service the generator for AC use?

Follow the manufacturer’s maintenance schedule, changing oil and filters every 200 hours when using a generator for frequent AC power supply.

The Bottom Lines

Generators are most important for a 4-ton AC unit. Not every generator is able to run AC units.

Your generator has to be powerful enough for a startup otherwise it will not be able to run a 4-ton AC. You must go for the right size generator for your 4-ton AC unit. 

Mark Allen

Mark, a certified electrician, simplifies electrical work. Trust his decade of experience for safe and effective electrical installations, wiring, and tool guidance.

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