There are two types of air compressors you should be concerned with. Both run on 12V direct current and are usually used to inflate the tires on cars and RVs. Of course, this is just a rough categorization of air compressors because we’re only interested in those that service vehicles. In the case of RVs, size matters.
Typical 12V DC Air Compressors
A small air compressor that comes with a lighter-style plug is at the bottom of the totem pole. This type of air compressor may use a few amps under full load. Its main use? Inflating tires rather slowly on regular passenger vehicles, motorcycles, etc.
If you’re talking about air compressors which can be clamped directly onto the vehicle’s battery then you’re talking about an air compressor fit for a motorhome. These types of compressors can draw more current under full load.
The reason they draw more is because they need extra power. They need it to inflate large or high-pressure tires which are commonly found on most RVs, trailers, and motorhomes in general.
You might also be able to tell how much an air compressor uses depending on how it’s labeled.
If you need an air compressor that can work continuously, you need one that runs on the house circuit.
Important Tip when Using an Air Compressor
Never forget to keep the engine running. The massive power draw of a running air compressor can quickly deplete the battery. If you keep the vehicle running, the battery can provide a consistent voltage to the compressor’s motor and it won’t fail you when you’re ready to hit the road again.
You know that there are both DC and AC compressors. Not all compressors are used in motorhomes so some of them are designed to work with regular household outlets which run on alternating current (AC).
But, there are also hybrid compressors. They can switch between AC and DC and can be used at home or on the road. Some of them have a high power draw while others only have a high power draw on the DC setting.
How to Pick an Air Compressor for Your RV
How many amps an air compressor uses is a valid question but not the one you should be asking yourself if you’re looking to buy one for your RV. There’s more to choosing the right air compressor than just the current draw rating.
First of all, an air compressor should be rather light and have a small footprint. That will make it easy to store it in some compartment until you need it. A lengthy extension hose and long battery clamps are also important, especially if you have a long RV.
Then you have to consider at how many PSI the air compressor can operate. Most motorhome owners prefer air compressors that can handle around 150 PSI. That shows that the storage tank can hold a lot of air and that you can inflate tires faster. It also shows that the air compressor can handle inflating high-pressure RV tires even when there’s a potential leak.
Don’t fall for advertising exaggerations. Most manufacturers try to lure people into buying expensive air compressors by listing them with a high HP rating.
The reason for this is simple. For a portable air compressor of, say 6HP, to operate at peak efficiency it would need to be plugged into a 240V outlet.
That’s not something you can do with a regular house outlet. Therefore, a 2HP air compressor is more than enough as long as it can inflate high-pressure tires.
One last thing to note is the CFM rating. CFM stands for cubic feet per minute and it tells you how fast the air compressor can push a specific volume of air. CFM ratings are usually rated at certain PSI ratings, i.e. 3 CFM at 90 PSI.
But, you may also encounter some misleading advertising with CFM ratings too. For example, some compressors may be rated for 3 CFM at 90 PSI. But that may only mean that the compressor can deliver 3 CFM by the time the pressure reaches 90 PSI. Of course, the CFM would change with pressure.
Power or Current Draw Is Not Your Only Concern
How many amps does an air compressor use? It depends on the type of compressor and what its intended use is. The majority of portable air compressors which you can use on an RV will rarely go near or above 12A under full load. Anything over that is going to trip the circuit breaker.
The conventional wisdom is that 1HP will require about 12A current.
You don’t have to worry as much about the power draw as you should be concerned about whether or not the air compressor has enough power to inflate high-pressure tires efficiently and in a timely manner.