Many factors affect the price of a compressor, including motor size, tank volume, and pressurization type. In general, a larger and more powerful compressor will be more expensive since it is designed for frequent, industrial use, such as in an automotive repair shop. Many hobbyists may not need this much power for basic air tool needs around the home, requiring a smaller compressor type.
An air compressor's motor performs the necessary job of moving outside air into the machine, allowing it to become more densely compacted within the tank for movement out to an attached air tool, like a grinder. The pumping power of the motor — also referred to as standardized cubic feet/minute (SCFM) — determines the machine's overall power output. Higher SCFM values indicate stronger air pumping action from the motor, thereby increasing the price tag. Many common hobbyist tools, like drills, only require small SCFM values that are typically found in less expensive compressor models.
The motor's assembly material also contributes to the price of a compressor. Inexpensive air compressors use an aluminum sheath surrounding the motor or pump. Although aluminum is strong, air compressors with cast iron assemblies offer longer motor life, but with a higher price tag. Consumers will need to weigh their everyday compressor needs against the compressor's price; more frequent compressor use would warrant the more expensive cast iron assembly for a longer service life.
Oil lubricated air compressors offer longer service life as well, but again have a higher price tag. Consumers who need an air compressor for infrequent use can purchase a less expensive oil free compressor. The oil free compressor will offer adequate functionality for occasional use without the oil change maintenance.
The price of a compressor is also affected by the tank's volume. Larger tanks hold more pressurized air reserves, allowing the user to have a constant supply of forced air while using tools. Small tanks cannot hold as much air, causing the compressor to periodically turn on and off to bring more air into the tank. The tank's size increases the price of a compressor mainly because of material costs during manufacturing.
These machines use either a one stage or multistage pressurization assembly, which also contributes to the price of a compressor. One stage mechanisms pressurize the air in one phase and store it for future use, making this compressor type relatively inexpensive. Multistage compressor types use two or more phases for pressurizing air, effectively compacting the air molecules more and more with each pressure period. As a result, more compressor stages make for a more expensive machine.