# Heat recovery from air compressors

The Compressed Air Challenge heat recovery fact sheet (May 2026) says as much as 80 to 93% of the electrical energy consumed by an industrial air compressor is converted into heat, and that a properly designed heat recovery system can often capture 50 to 90% of it for heating air or water.

## Uses for the recovered heat

Compressed Air Systems Fact Sheet #10 (May 2026, Rev. 01) lists typical uses: supplemental space heating, industrial process heating, water heating, makeup air heating and boiler makeup water preheating. The recoverable heat is generally not hot enough to be used directly for steam production. Heat recovery systems are available for both air-cooled and water-cooled compressors. The 2016 edition of the US Department of Energy sourcebook gives the same 80 to 93% and 50 to 90% figures.

## Hot air from air-cooled rotary screw compressors

In air-cooled packaged rotary screw compressors, ambient air is heated as it passes across the aftercooler and the lubricant cooler. Because packaged compressors are typically enclosed in cabinets and already include heat exchangers and fans, the fact sheet says the modifications needed are ducting and another fan to handle the duct loading. A thermostatically controlled hinged vent modulates the system, and when heating is not required, such as in the summer months, the hot air can be ducted outside the building. The hot air can serve space heating, industrial drying or preheating aspirated air for oil burners.

As a rule of thumb, approximately 50,000 Btu per hour is available for each 100 cfm of capacity at full load, and recovery efficiencies of 80 to 90% are common. The fact sheet cautions that if the compressor supply air does not come from outside and the heat is used in another space, cabinet static pressure and compressor efficiency can drop; if outside air is used, some return air may be needed to avoid damaging the compressor with below freezing air.

## Hot water and water-cooled compressors

A heat exchanger on the lubricant coolers of packaged water-cooled reciprocating or rotary screw compressors can produce non-potable (gray) or potable water, for central heating or boiler systems, industrial cleaning, plating, heat pumps or laundries. Heat recovery for space heating is less common with water-cooled compressors, because an extra stage of heat exchange is required and the available heat is at a lower temperature; typical recovery efficiencies are 50 to 60%.

## Estimating the savings

The fact sheet compares heat recovery with the current source of thermal energy, which may be a low-price fossil fuel such as natural gas, and estimates annual energy savings from recovering heat for space heating from an air-cooled rotary screw compressor as 0.80 × compressor bhp × 2,545 Btu/bhp-hour × hours of operation.

### Can compressor heat produce steam?

Generally not. The Compressed Air Challenge fact sheet (2026) says recoverable heat from a compressed air system is generally not hot enough to be used directly for steam production.

### How much heat does an air-cooled screw compressor give?

As a rule of thumb, the fact sheet gives approximately 50,000 Btu per hour for each 100 cfm of capacity at full load.

## Sources

- [Compressed Air Challenge, Compressed Air Systems Fact Sheet #10: Heat Recovery with Compressed Air Systems (May 2026, Rev. 01)](https://www.compressedairchallenge.org/data/sites/1/media/library/factsheets2026/fact-sheet-10-heat-recovery-with-compressed-air-systems_updated2026.pdf)
- [US Department of Energy and Compressed Air Challenge, Improving Compressed Air System Performance: A Sourcebook for Industry, Third Edition (2016), Fact Sheet 9](https://www.energy.gov/sites/prod/files/2016/03/f30/Improving%20Compressed%20Air%20Sourcebook%20version%203.pdf)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/industry/compressor-heat-recovery/