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Will a 3500 Watt Generator Run an Air Conditioner?


When sweltering summer days arrive, keeping your home cool is a top priority. Air conditioning units are lifelines, but what if a power outage strikes during a heatwave? Can a 3500-watt generator step up and keep your air conditioning unit running?

Here, we’ll explore the factors determining whether a 3500-watt generator has the power required to start up your AC unit and address questions like how big of an air conditioner it can handle, how long it will run, and what size generator you might need for effective cooling.

Will a 3500 Watt Generator Run an Air Conditioner?

If you’re asking, “Will a 3500-watt generator run an air conditioner?” Well, it depends on several factors. It includes how much power an AC unit requires, the starting and running wattage of the generator, and the specific model and efficiency of the generator and the air conditioner.

Here’s what you need to consider:

Air Conditioner Power Requirements

Check the air conditioner’s specifications to find the running (continuous) and starting (surge) wattage. Air conditioners often require a higher wattage when they start up due to the compressor kicking in.

Generator Starting and Running Wattage

Ensure that the power output of a 3500-watt generator can provide both the starting and running wattage required by the air conditioner. If the starting wattage is the same amount or significantly higher than 3500 watts, the generator may struggle to handle it.


Generators have varying degrees of efficiency, and some models may handle high starting loads better than others. A generator with inverter technology is generally more efficient and better suited to handling appliances with sensitive electronics like air conditioning units.

Other Loads

Consider what other electrical devices are running on the generator simultaneously. If you’re using the generator to power multiple appliances simultaneously, it may not have enough capacity to handle the air conditioner and other loads.


Air conditioner usage varies with the climate. ACs may run more frequently in extremely hot conditions, requiring more power.

Extension Cords and Wiring 

Ensure you use appropriate extension cords and wiring to connect the air conditioner to the generator. Inadequate wiring can lead to power loss and potential damage to the appliances.

Generally, a 3500-watt generator can run a small to medium-sized air conditioner with lower starting wattage requirements. However, you may need a larger generator if your air conditioner has a high starting wattage. It’s essential to check the specifications of both your generator and air conditioner and, if necessary, consult the manufacturer or an electrician to ensure safe and reliable operation.

How Big of an Air Conditioner Can a 3500 Watt Generator Run?

ACs come in various sizes, and their power consumption depends on factors such as cooling capacity. Here are some general guidelines:

Small Portable or Window Air Conditioners 

A small portable and window air conditioner typically requires 1000 to 2000 watts. A 3500-watt generator should comfortably run these ACs.

Medium-Sized Room ACs 

Units with a cooling capacity of 8000-12,000 BTUs generally need 2000 to 3000 watts. A 3500-watt generator might work if you limit other electrical loads while the air conditioner is running.

Larger Central Air Systems

These can require 3500 to 5000 watts or more. A 3500-watt generator may not be sufficient, especially if it lacks the necessary surge power to start the compressor.

How Long Will a 3500-Watt Generator Last?

The runtime of a 3500-watt generator on a single fuel tank depends on the generator’s fuel efficiency and the load it carries. It’s important to check the generator’s specifications for its runtime at a given load and the size of its fuel tank. 

On average, a 3500-watt generator can run for about 3 to 6 hours on a full tank under a moderate load, which should cover most residential air conditioning needs during a power outage.

What Size Generator Do You Need to Run an AC?

To determine the generator size required to run your air conditioner effectively, consider the following:

Consult Your Air Conditioner’s Specifications

 Check your air conditioner’s user manual or label for its continuous and surge wattage requirements.

Account for Surge Power

Ensure the generator can handle the initial power surge when the air conditioner starts. This surge can be considerably higher than the running watts, so choose a generator with enough extra capacity.

Consider Additional Loads

If you’re using multiple devices simultaneously, sum up their wattage requirements and add them to the air conditioner’s needs.

Inverter Generators

Consider using an inverter generator, which provides cleaner power and can better handle sensitive electronics in your air conditioner.

Final Thoughts

Running an air conditioner on a 3500-watt generator is possible, but the key to success lies in understanding your specific air conditioner’s power requirements and the generator’s capabilities. Smaller air conditioners with lower wattage demands are more likely to be compatible with a 3500-watt generator, whereas larger central air systems might require a generator with greater capacity.

Before relying on a generator to power your air conditioner, consult the manufacturer’s specifications for both the generator and the air conditioner and consider other appliances you plan to use simultaneously. Doing so can ensure that you’ll stay cool and comfortable during power outages without overloading your generator.

JP Reyes

JP has been in the aircon industry for almost as long as he has been alive. As a child JP would help his tatay fix aircon units at their junk shop in Cavite. After graduating UP in the early 2000's, JP then started his own Aircon servicing business and within 5 years had 10 shops in 8 different cities. Fast forward to today and JP brings all his experience and expertise online to give readers trustworthy advice and reviews about Air-conditioning buying, servicing, cleaning and repair in the Philippines.

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