The size wire that you will need for an extension cord for a small air conditioner depends on the amperage of your air conditioner.
To ensure that you can safely use an extension cord with your air conditioner, the wires need to be able to handle the current and power that the air conditioner draws.
Different sizes or gauges of wires can handle varying ranges of amperages, but a 14-gauge extension cord should be suitable for a small air conditioner.
Air conditioner and extension cord safety
Some air conditioners come with an extension cord when you buy the units, but many do not. This is because air conditioners use a lot of power to start up and operate.
In fact, air conditioners use about double the amount of power that they normally do when they are first starting up to get the system up and running.
This means that there will be a lot of current and power running through the extension cord, and this will translate into a lot of heat, which can be dangerous. This is why it is important that you find the right extension cord for your air conditioner, even if it is small.
What size wire for small air conditioner extension cord?
If you want to find the right extension cord for your air conditioner, there are a few factors to consider. Some of the most important factors include:
- Finding an extension cord with the right wire size
- Finding an extension cord with the right power capacity
- Finding an extension cord with the right connector
Finding an extension cord with the right type of connector for your power outlet and air conditioner power cord is simple, as you just need to ensure that the cord is compatible.
This is also true in terms of power capacity, as you only need to ensure that the extension cord is compatible with the wattage, voltage, and amperage of your air conditioner model.
However, finding the right wire size can be slightly more complicated. Since air conditioners need so much power to start up and operate, you need to ensure that the wire gauge can handle this vast amount of current.
Estimations for the amperage-to-wire-size conversions are as follows:
| Wire size | Amperage |
| 14-gauge wire | 15 to 20 amps |
| 12-gauge wire | 20 to 25 amps |
| 10-gauge wire | 30 to 35 amps |
You should work out the amperage of your air conditioner in order to determine what size wire you need.
Your extension cord wire will have to be able to handle about double the current that your air conditioner specifies, because of the higher power that the unit draws to switch on initially.
How to calculate the amperage of your air conditioner
Although most guidelines suggest that a 12-gauge wire is best for high-power appliances such as air conditioners, even though a 14-gauge wire will work in most cases, the best way to be sure is to calculate the amperage of your air conditioner and compare this to the figures in the table above.
To do this, you need to divide the wattage of your air conditioner by its voltage. This information is usually printed on the manufacturer’s label or in the owner’s manual of the unit.
If the amperage is on the label as well, you can use the amperage listed. Remember to double this amount to ensure that the extension cord can handle the initial power draw safely.
How many amps does a small air conditioner use?
In order to illustrate this point further, it can be useful to examine the amperage of real-life small air conditioners and which size extension cords are suitable for them, as follows:
| Small air conditioner | Amperage | Appropriate wire size for extension cord |
| GE 5,100 BTU Portable Air Conditioner for Small Rooms | 7.4 A
(850W ÷ 115V) |
14-gauge wire |
| GE Window Air Conditioner 5000 BTU | 3.9 A
(455W ÷ 115V) |
14-gauge wire |
| GE Electronic Window Air Conditioner 6000 BTU | 4.6 A
(535W ÷ 115V) |
14-gauge wire |
This shows that in the case of smaller air conditioners, 14-gauge extension cord wires are safe to use, even if 12-gauge wires are recommended by most experts.
The best extension cords to use for air conditioners
To ensure that the extension cord you want to use is safe to use with your air conditioner, it is safest to use an extension cord that was specifically designed to be used with high-power appliances, such as:
| Extension cord | Where to buy | Length | Wire size | Price |
| Heavy Duty Air Conditioner and Major Appliance Extension Cord Wire |   |
12 feet | 14-gauge | $17.99 |
| Buy it on Amazon | ||||
| POWTECH Heavy duty Air Conditioner and Major Appliance Extension Cord |   |
12 feet | 14-gauge | $15.39 |
| Buy it on Amazon |