Compressed air is vital to many operations both industrial and otherwise, so you want to make sure you buy a compressor with enough power to meet your needs. If you want to know what horsepower you should get for an air compressor that can handle all your applications, it helps to start with an understanding of what that number means.
Understanding Air Compressor Horsepower
When shopping for a new air compressor, many customers look to its horsepower rating to get a sense of how much power it can provide. The reason for this is understandable — most of us are familiar with horsepower ratings and use them as a factor when buying a car, lawnmower or other equipment.
The truth is, however, that horsepower ratings don’t tell the whole story when it comes to what a compressor can and can’t do. Instead, a compressor’s horsepower is just one rating that should be considered when shopping for a new unit. In fact, it may even be one of the least significant.
What Is Horsepower?
Horsepower is a measure of the amount of work an engine can perform. Several different definitions exist for the term. Car aficionados are likely to be aware of the distinction between standard horsepower (HP) and brake horsepower (BHP), which is the measure of a motor’s power without any of the losses incurred by running auxiliary engine components. Most of the time, when we talk about horsepower in a more abstract sense, we are talking about a unit of power equivalent to 550 foot-pounds per second, or 745.7 watts.
All compressors have a motor component that is rated in horsepower. A compressor motor’s job is simply to drive the cylinders or rotary screw that compress air. The process by which this occurs is complex. As a result, the relationship between the amount of horsepower a motor has and the amount of work a compressor can do is not always straightforward.
HP vs. CFM vs. PSIG
Horsepower (HP), pressure (PSIG) and capacity (CFM) are the three main measurements of what a compressor can do. PSIG is a measure of air pressure. To work properly, most air-powered tools require at least 90 PSIG. CFM refers to the maximum amount of air a compressor can produce at a given pressure level. To run multiple air powered tools at once, a higher CFM rating is required.
When all other factors are equal, horsepower is a measure of the compressor motor’s efficiency at producing a given level of CFM and PSIG. For example, if a 5 HP air compressor and a 10 HP air compressor can both produce 100 PSIG of air pressure at a rate of 15 CFM, the 5 HP model is working more efficiently, saving you money on fuel without a loss in performance.
There are, of course, limits to this efficiency. Most well-designed compressors produce approximately 4 CFM at 100 PSIG per unit of horsepower.
How Important Are Horsepower Ratings When Shopping for a New Compressor?
A compressor’s horsepower rating is an important measure of what it can do and how well it can do it. Under no circumstances will a 5 HP air compressor be able to do the same job as a 100 HP air compressor. However, it is important to remember that horsepower alone shouldn’t be the only factor you consider. The “best” 5 HP air compressor may not be the right one for you if it doesn’t deliver the CFM or PSIG you require of it.
Other Factors to Consider
When you’re shopping for a new air compressor, there are a few additional factors to consider, such as portability. Portable air compressors come in a variety of shapes and sizes. Many are light enough to carry, while larger models have wheels so they can be easily transported. Tank sizes for portable air compressors range from 2- to 30-gallon capacities for light-duty to more demanding jobs.
Stationary air compressors are designed to be bolted to a fixed area and wired directly into your electrical circuit. With larger tanks and greater horsepower, stationary air compressors are ideal for workshops and garages.
The tank size of your air compressor also determines the scope of work you can accomplish. Air compressor tank size can range from 2- to 80-gallon capacities. If you’re using tools that require a high volume of air for continuous use, a larger tank is an ideal choice. However, if your tools only use quick bursts of air, the tank will drain much more slowly, so a capacity of 2 to 6 gallons will likely be sufficient.
What Horsepower to Get for an Air Compressor
Air compressors typically have a horsepower rating between 1.5 and 6.5, though some larger, stationary air compressors can have up to 15 HP. If you are using standard electric power outlets, you’ll need an air compressor at 2 HP or less because standard AC cords require lower voltage to function.
The type of air compressor you get also affects the horsepower ratings. If you were running an electric air compressor at 5 HP, you would need to run a gas- or diesel-powered air compressor at 10 HP to do the same amount of work as the electric model. This is because a gas engine actually produces power through its own combustion, while electric motors draw their power from an external system.
Quincy Compressors has a complete selection of 5 HP, 10 HP and larger air compressors for sale. Check out our Resources page for detailed technical information about our horsepower ratings or contact a sales representative for assistance.