If you’re going to use your compressor outdoors, or move it around quite a bit, you’ll want to choose a portable air compressor. Portable air compressors use gasoline or diesel engines, instead of electric power. One drawback of portable air compressors is that the internal combustion engines greatly increase the noise and heat they generate. However outdoors or on a remote job site, this isn’t usually a major drawback. In addition, gasoline or diesel compressors are usually cheaper to operate than electric compressors.

When evaluating portable air compressors, you’ll want to pay careful attention to the total weight, wheels, and handles each model uses. Larger portable air compressors for construction are often self-contained trailers, making it easy to move them from job site to job site.

Note that portable air compressors are most commonly rated by horsepower instead of CFM (cubic feet per minute) or PSI (pounds per square inch), which are the actual ratings you should be evaluating. A small home air compressor might produce 1.5 HP while large portable compressors generate hundreds of HP. The rule of thumb you can use to determine your approximate needs is that 1 HP should produce 4 to 5 CFM.

However, you don’t need to worry much about horsepower when you’re shopping. Instead, focus on the CFM and PSI specifications of your tools. Total the CFM requirements of all your tools and multiply by 1.5 to build in a margin of safety, and just use the single highest PSI requirement as your benchmark.