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.
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.