Air-cooled vs Water-cooled compressor
Air compressors generate heat as they work, so compressed air needs to be cooled with air or refrigerated liquid.
Whether your business chooses a water-cooled compressor or an air-cooled compressor depends on your commercial space’s location, tools, and size. Learn some comparisons between air-cooled vs. water-cooled compressors to help you decide.
How does an air-cooled compressor work?
Air-cooled compressors use air to decrease the temperature of the compressed air and any other materials present. When the compressor heats up, the air cooling circuit reduces the hot air through the fan and radiator. Air-cooled compressors are the most common cooling system and are easier to use than water-cooled systems.
Industry can save utility bills by using the energy to heat buildings or power preheating batteries to recover heat losses from air-cooled compressors. The circuit directs heat to the area with the fan, but if the building doesn’t need more heat, the unit releases the warm air into the atmosphere, controlled by a thermostat or air damper.
How does a water-cooled compressor work?
The compressed air and any other materials present during compression are cooled using liquid coolant from an external unit in water-cooled compressors. The cooling circuit reduces heat through shell and tube exchangers, which transfer heat from the compressed air into the liquid coolant circuit—a mechanism that distinguishes water-cooled designs from the fan-and-radiator setups used in air-cooled compressors. Water cooling is more common on higher-horsepower machines, and the cooling water itself removes approximately 90% of the heat energy generated by the compressor’s electric motor, which eases ventilation requirements around the equipment.
Companies can reuse the water the compressors produce in hot water heating systems, typically for showering, cleaning, or washing. A water-cooled compressor can allow a business to invest in a smaller water heater since you won’t need as much hot water.
Why does your air compressor need a cooling system?
Air compressors need cooling because compression generates heat that must be removed before the air moves downstream.
In oil-injected rotary screw air compressors, most of the heat is removed internally by circulating oil (also known as coolant). The air leaving the compressor is very hot and must be cooled before it goes downstream; typical outlet temperatures for oil-injected screw compressors can exceed 160°F. Discharge temperatures from oil-free air compressors or two-stage reciprocating compressors may be 300-350°F. These high temperatures can cause problems downstream in compressed air systems, especially air dryers.
Air dryers are rated for inlet temperatures no greater than 100°F. When the temperature is high, the dryer does not work effectively. Warmer air carries more moisture, stressing the drying system. If the dryer doesn’t remove enough moisture, it can cause condensation to form in other parts of the distribution system as the air cools. Too much heat can cause other problems:
Excessive heat can degrade seals and wash away lubricant in downstream tools and equipment, leading to premature failure of system components.
Failure to control the heat generated by air compression will heat the compressor room and surrounding environment, potentially causing the air compressor itself to overheat.
If the compressor is running indoors, the excess heat generated by the compressor can stress the air conditioning system in summer.
Energy costs for air cooling vs. water cooling
When considering the energy costs of each air compressor cooling system, you should keep the following factors in mind:
Energy consumption
Air-cooled units typically draw slightly more electricity than water-cooled units of the same capacity, because fans must move large volumes of air.
Total cost
However, water-cooled systems add ongoing costs for water supply, treatment, and cooling-tower electricity — which usually outweigh the fan-power savings. Once water and treatment are factored in, air-cooled units generally have the lower total operating cost.
Ability to recover resources
Compressor cooling systems provide reusable resources to compensate for energy bill costs. If you can reuse water from your water-cooled compressor to preheat your boiler, you can save on gas and heating bills. You can also use the hot air from an air-cooled compressor to warm a room and power a fluid heat exchanger.
Air-cooled compressor requirements
Air-cooled compressors require sufficient cooling air and space to provide adequate airflow. Insufficient inlet or discharge space can cause temperature regulation issues that result in nuisance shutdowns or equipment failures, leading to unplanned downtime if the compressor room gets too hot.
To protect your equipment and continue your workflow, install ductwork from both sides of the compressor so air can circulate throughout the space. If your business needs more space for additional equipment, setting up a water-cooled compressor is best.
Water-cooled compressor requirements
Water-cooled compressors require high-quality cooling water to function. If you get your water from a lake, ocean, well, or river, you need cooling towers and a closed-loop system to filter the water, protect water quality, and prolong the system’s life.
Unless your building already has this equipment, you will need to include the cost of purchasing, installing, and maintaining this new machine and the water-cooled compressor. If you have a closed-loop cooling system on the site, ensure it can accommodate your water-cooled compressor before installing it.
Water-cooled systems generally fall into three types—open, recirculating, and closed-loop—each offering different tradeoffs between water consumption, installation complexity, and heat dissipation efficiency, with closed-loop designs typically favored for minimizing water usage in continuous industrial operation. Open systems can draw from natural sources such as ponds, rivers, lakes, or wells instead of municipal water, but regional discharge restrictions may require a closed-loop configuration instead.
Which system should you choose?
Air compressors can serve a variety of industrial applications, but you need to choose the best type for your particular business. Here are some factors to consider when looking for a suitable air compressor:
Operating and resource costs
With the cost of water conditioning on the rise, it is essential to consider how much you will pay to use and maintain your equipment. Since water-cooled air systems use more water to reduce the heat of the air, they tend to be more expensive to operate, though the exact cost impact varies by installation. Air-cooled compressors do not use as much water to power their products, and in general, some models offer lower upfront and installation costs compared to water-cooled alternatives.
Air demand requirements
Evaluate the compressor’s cubic feet per minute (cfm) rating, horsepower (hp), and pounds per square inch (psi) rating. Horsepower indicates capacity for high air demands; The cfm rating tells how much air the compressor can easily produce per minute to give you the proper psi. Look at cfm and psi ratings to determine which will meet your tool and energy requirements.
The type of tool used in your industry
Consider the horsepower requirements of your equipment and find out which cfm and psi ratings are suitable for your air compressor.
The layout of the compressor room
Before choosing an air compressor, ensure the room has enough space. If space is an issue, you can purchase several smaller compressors and place them in multiple areas around the plant instead of purchasing one large compressor. Lower-horsepower rotary screw compressors are typically only available in air-cooled configurations, limiting water-cooled options for smaller installations.
Compressor room ventilation
Air-cooled compressors require adequate airflow to operate and regulate temperature, and they generally need ample space to prevent overheating. If the room is not adequately ventilated, the area may become too hot, and equipment may shut down, delaying the project. Position air-cooled compressors away from heat sources such as boiler rooms. For consistent operation, select a larger unit; for intermittent use, a smaller unit may suffice. Water-cooled compressors are suited for tight spaces and higher temperatures, and they’re typically used in higher horsepower machines where heat loads are greater.
That said, water-cooled systems aren’t automatically the right choice just because they handle heat well. Facilities lacking a dedicated water line, a treatment system, and return or recirculation infrastructure are generally unsuited for water-cooled compressors regardless of their heat-load advantages. Without these in place, the added plumbing and maintenance requirements can outweigh the cooling benefits, making an air-cooled unit the more practical option despite its space and airflow demands.
Air-cooled vs water-cooled comparison table
With cooling requirements, room layout, and ventilation now covered, the table below consolidates the key differences into a single reference for quick decision-making.| Factor | Air-Cooled | Water-Cooled |
|---|---|---|
| Cooling medium | Ambient shop air pulled through fans / fins | Circulated water (once-through or closed-loop) |
| Clearance / space needed (75 HP screw example) | 36 inches on all sides for airflow | Up to 10 GPM in a closed-loop supply line; smaller physical footprint at large capacities |
| Aftercooler discharge temperature | Air temperature roughly 15-20°F above ambient | Air temperature roughly 10-15°F above water temperature |
| Discharge temperature / pressure ceiling | Handles discharge temperatures up to 350°F and pressures up to 250 PSI | Can manage discharge temperatures up to 450°F and pressures up to 435 PSI |
| Performance in hot / high-pressure conditions | Cooling efficiency drops as ambient climbs past 90-100°F or pressures exceed 250 PSI | Maintains tighter temperature control in the same conditions |
| Dust / dirt resistance | More exposed to fouling on fins and coolers | More resistant to dirt and dust buildup |
| Water / water-treatment needs | None | Requires water supply, and treatment/quality control for closed-loop or tower systems |
| Total operating cost (all-in) | Typically lower once water, treatment, and cooling-system electricity are included | Typically higher due to added water and treatment costs |
| Heat recovery potential | Limited to none | Heated water can be redirected to process heating or hot water use |
| Installation complexity | Simpler — no piping / tower needed; a self-contained, fan-based design | Requires heat exchangers and, in many cases, a cooling tower, which means more installation planning and utility connections |
Real-world facility scenarios for cooling choice
The scenarios below show how the factors already discussed — climate, airflow, water access, and heat recovery — play out in actual facilities.
| Facility condition | Better-suited system |
|---|---|
| High ambient heat / humidity, poor ventilation | Water-cooled |
| Moderate climate, strong ventilation, no water source | Air-cooled |
| Existing process water or heat-recovery need | Water-cooled |
| Limited floor space for tower / piping | Air-cooled (unless compact water-cooled footprint fits) |
When considering these factors, remember that neither type of air compressor is universally superior. Your choice of air-cooled or water-cooled compressor will depend on your specific application and location. Discuss your options with BISON before deciding which suits your industry.
frequently asked questions about Air-cooled vs Water-cooled Compressor
How do air-cooled vs water-cooled air compressors affect energy costs?
Water-cooled units require less electricity than air-cooled compressors. Still, customers should also consider the cost of electricity for the cooling system, water, and water treatment costs when choosing a water-cooled unit. Air-cooled compressors are usually more cost-effective once these expenses are factored in.
On the other hand, some customers use cooling water to preheat factory processes, such as boilers, to save on gas and heating bills.
What are the applications of air-cooled air compressors?
Air-cooled compressors are the standard choice for most general industrial use — powering pneumatic tools such as jackhammers, drills, and impact wrenches, filling cylinders, and operating assembly lines. They suit facilities with good ventilation where the compressor room stays cool. Their exhaust heat can also be ducted to warm adjacent spaces in winter, recovering some energy that would otherwise be wasted.
What are the applications of water-cooled air compressors?
- It is used where there is a lot of water.
- Therefore, it can be installed near water bodies such as lakes or rivers.
- It is also used to heat buildings.
Does the water-cooled compressor need to purchase a cooling water tower?
Water-cooled compressors need cooling water; that's obvious, right? Water quality is also an issue. The better the water quality, the longer the compressor heat exchanger will last. So you typically see closed-loop cooling systems that control water quality rather than city water. Purchasing these additional devices with on-site closed-loop cooling systems may only make sense. Purchasing a closed-loop system with a cooling tower will significantly increse the capital cost of purchasing a new compressor. The system's operating cost must then be added to the operating price of the compressor, further expanding the lifetime cost of the compressor. Many large plants already have cooling towers for other equipment, so it becomes a question of whether the cooling tower can provide the required flow with excellent water quality.
