What Are the Top Types of Chiller Systems?

Choosing a chiller system is not just a matter of comparing nameplate efficiency. Building size, climate, operating hours, water availability, and maintenance capacity all shape the right choice. Common options include air-cooled and water-cooled chillers, alongside centrifugal, screw, scroll, and absorption designs. Each has trade-offs.

The International Energy Agency’s The Future of Cooling report found that global energy demand for space cooling had tripled since 1990. It projected another near-tripling by 2050. That forecast covers cooling broadly, not chillers alone, but it shows why careful system selection matters. The U.S. Department of Energy’s Federal Energy Management Program also sets chiller efficiency criteria by equipment type and capacity. Comparing models therefore requires matching the correct category and rating conditions.

Energy-efficiency expert Amory Lovins is widely credited with the phrase, “The best energy is the energy you don’t use.” For chiller planning, that idea points toward reducing cooling loads before oversizing equipment. Still, it is not a complete selection rule. A smaller unit can struggle on the hottest afternoon, while an oversized one may cycle inefficiently during mild weather. The details matter. This guide compares the top chiller system types, explains where each performs well, and highlights the practical compromises behind the specifications. A chart cannot replace a site assessment; real buildings are rarely as tidy as their load estimates.

Table of Contents [Hide]

1 Chiller Capacity and Ratings: 1 Refrigeration Ton Equals 3.517 kW

2 Air-Cooled Chillers: Compare AHRI 550/590 IPLV and kW/ton

3 Water-Cooled Chillers: Compare Chiller, Cooling-Tower, and Pump Energy

4 Absorption Chillers: Typical COP—0.6–0.8 Single-Effect, 1.0–1.2 Double-Effect

5 Compressor Chillers: Compare Scroll, Screw, and Centrifugal Designs by Capacity

Chiller Capacity and Ratings: 1 Refrigeration Ton Equals 3.517 kW

What Are the Top Types of Chiller Systems?
Chiller Capacity and Ratings: 1 Refrigeration Ton Equals 3.517 kW

A refrigeration ton measures cooling capacity, not a machine’s electrical consumption. One ton equals 12,000 Btu per hour, or about 3.517 kW of cooling. NIST’s Guide for the Use of the International System of Units provides the conversion basis; the extra digits matter when checking specifications. Small rounding differences are normal.

For example, a 100-ton chiller provides roughly 351.7 kW of rated cooling. That does not mean it draws 351.7 kW from the electrical supply. Power input depends on operating efficiency, commonly expressed through COP or kW per ton. AHRI Standard 550/590 sets procedures for rating water-chilling packages under specified conditions, helping buyers compare equipment on a consistent basis.

Real buildings rarely hold those conditions all day. Water temperatures, condenser conditions, and load can shift as outdoor temperatures change. A chiller rated at 100 tons may deliver less under demanding site conditions. Check the rating conditions and part-load data, not just the headline number. Easy to overlook. Even a careful estimate can mislead if actual flow or temperature readings are poor.

Air-Cooled Chillers: Compare AHRI 550/590 IPLV and kW/ton

For air-cooled chillers, AHRI Standard 550/590 provides a common way to compare part-load performance. Its Integrated Part Load Value (IPLV) weights efficiency at four load points: 1% at full load, 42% at 75%, 45% at 50%, and 12% at 25%. The weighting reflects a standardized operating profile, not every building’s actual schedule. Useful, but incomplete.

Kilowatts per ton (kW/ton) gives a direct efficiency figure at a specific test condition. Lower is better.

Using the standard conversion of 12,000 Btu per refrigeration ton and 3,412 Btu per kilowatt, 1.20 kW/ton equals about 2.93 COP.

Compare figures only when entering-water temperature, outdoor air temperature, and load conditions match. A full-load rating cannot fairly be set beside an IPLV.

For procurement, ask for both the AHRI-certified IPLV and the kW/ton values at relevant operating points. A chiller with a strong IPLV may still use more energy at a site that runs near full load. Conversely, mild-weather operation can make part-load performance especially important. AHRI’s rating method improves apples-to-apples comparisons, but actual energy use also depends on pumps, fans, controls, and local weather. The gap can be noticeable. Cite AHRI Standard 550/590 for rating definitions, and document the test conditions alongside every quoted efficiency figure.

Water-Cooled Chillers: Compare Chiller, Cooling-Tower, and Pump Energy

Water-cooled chiller efficiency is not just a compressor number. The cooling tower fans and water pumps also draw power, so compare the whole plant under the same cooling load. A chiller may look efficient on its own while the tower or pumps quietly use more electricity than expected.

Measure each component separately. The chiller’s compressor responds to cooling demand and condenser-water temperature. Tower fans work harder on hot, humid days, while condenser pumps move water between the chiller and tower. Chilled-water pumps serve the building loop and may run longer than necessary if valves or controls are poorly adjusted. Small details matter: a clogged strainer or an unnecessarily high pump setting can add load.

Use meters to record chiller, tower, and pump energy alongside cooling output, ideally across different weather and operating conditions. Compare total plant energy per unit of cooling, not just the chiller’s rating. Part-load readings are especially useful. Still, field data can be messy: meters may be uncalibrated, and changing weather makes comparisons imperfect. That uncertainty should be noted, not ignored. A brief review of operating schedules and pump speeds can reveal practical savings.

Absorption Chillers: Typical COP—0.6–0.8 Single-Effect, 1.0–1.2 Double-Effect

Absorption chillers turn heat into cooling, so their COP compares cooling output with thermal input. Single-effect units typically deliver a COP of 0.6–0.8. The U.S. Department of Energy’s “Absorption Chillers for CHP Systems” fact sheet gives about 0.7 as a representative value. In practical terms, that is roughly 0.7 units of cooling per unit of heat supplied. A gas burner or recovered steam may provide that heat. Less heat.

Double-effect machines typically reach a COP of 1.0–1.2. The same DOE fact sheet reports about 1.2, while ASHRAE’s Handbook—HVAC Systems and Equipment explains how operating temperatures and design affect performance. Double-effect systems use higher-temperature heat and additional heat-recovery stages. Still, a tidy COP number can mislead. Cooling-tower water temperature, part-load operation, and pump power all shape real plant performance. When comparing proposals, check whether the quoted COP includes electrical auxiliaries and which temperatures were assumed. A chiller rated at 1.2 may not hold that figure through a hot afternoon or a changing load.

What Are the Top Types of Chiller Systems? - Absorption Chillers: Typical COP—0.6–0.8 Single-Effect, 1.0–1.2 Double-Effect

Absorption chiller type	Typical thermal COP	Typical driving heat	Common working pair	Typical application	Key consideration
Single-effect	0.6–0.8	Low-grade hot water or low-pressure steam; can also use recovered waste heat	Usually lithium bromide–water for chilled-water cooling	Buildings or facilities with suitable waste heat, hot water, or steam	Lower heat-source requirements, but typically lower COP than a double-effect cycle
Double-effect	1.0–1.2	Higher-temperature steam or direct-fired heat, depending on the design	Usually lithium bromide–water for chilled-water cooling	Sites with reliable higher-grade heat or fuel and a substantial cooling load	Higher COP than single-effect, but requires a higher-grade heat source and more complex equipment

Note: COP values are indicative thermal COPs (cooling output divided by heat input). Actual performance depends on the heat-source temperature, cooling-water conditions, chilled-water temperatures, and equipment design. Lithium bromide–water systems are commonly used for air-conditioning; ammonia–water systems are used where subzero refrigeration is required.

Compressor Chillers: Compare Scroll, Screw, and Centrifugal Designs by Capacity

Compressor chillers differ most in the capacity range they serve, their part-load behavior, and the space their equipment requires. ASHRAE’s 2020 Handbook—HVAC Systems and Equipment describes overlapping applications, not rigid capacity cutoffs. As practical selection bands, scroll units commonly serve about 10–200 tons, screw units about 100–1,000 tons, and centrifugal units from roughly 300 tons upward. Actual limits depend on configuration and operating conditions.

Scroll chillers suit smaller buildings, such as clinics or hotels, where modular units can fit through a service doorway. They are relatively simple, but several units may be needed as loads grow. Screw chillers often bridge the gap. Their capacity control can handle changing loads in campuses or mid-sized plants, though sound and vibration deserve attention near occupied rooms. Centrifugal machines are common in large plants with steady, high cooling demand. They can deliver high capacity in a compact footprint, but low-load operation and surge risk need careful review. Fit matters.

These ranges are not procurement guarantees. A 2023 AHRI Standard 550/590 rating compares water-chilling performance under defined test conditions; actual site efficiency shifts with entering-water temperature, fouling, and operating hours. Compare selection data at the expected conditions, not only nominal tons. A common mistake is sizing for the hottest afternoon alone. That can leave equipment cycling inefficiently through milder weeks. Real load profiles matter, and early estimates are often imperfect.