How to Buy an Energy-Efficient Commercial Unitary Air Conditioner
Information about energy-efficient unitary air conditioners in this section includes the following:
| Efficiency Recommendation Cost-Effectiveness Example Calculate Costs How to Select Sizing |
 |
Heating Options Technology Options Installation and Maintenance Environmental Tips For More Information |
Also provided is a portable document format version of How to Buy an Energy-Efficient Commercial Unitary Air Conditioner (PDF 181 KB, 2 pp). Download Adobe Reader.
| Efficiency Recommendation | ||
|---|---|---|
| Product Type and Sizea | Recommended Level | Best Available |
| <65 MBtu/h (3 phase) | 12.0 SEER or moreb | 14.5 SEER |
| 65 - 135 MBtu/h | 11.0 EER or more 11.4 IPLV or more |
11.8 EER 13.0 IPLV |
| >135 - 240 MBtu/h | 10.8 EER or more 11.2 IPLV or more |
11.5 EER 13.3 IPLV |
a Only air-cooled single-packaged and split system units used in commercial buildings are covered. Water source units are not covered by ENERGY STAR® but look for efficiency ratings that meet or exceed these levels for air source units.
b When operating conditions are often close to rated conditions or in regions where there are high demand costs, look for units with the highest EER ratings that also meet or exceed this SEER.
EER (energy efficiency ratio) is the cooling capacity (in Btu/hour) of the unit divided by its electrical input (in watts) at the Air Conditioning and Refrigeration Institute's (ARI) standard peak rating condition of 95°F.
SEER (seasonal energy efficiency ratio) and IPLV (integrated part-load value) are similar to EER but weigh performance at different (peak and off-peak) conditions during the cooling season.
| Cost-Effectiveness Example 120 MBtu/h - 10 Tons | |||
|---|---|---|---|
| Performance | Base Modela | Recommended Levelb | Best Available |
| EER / IPLV | 8.9 / 9.2 | 11.0 / 11.4 | 11.8 / 13.0 |
| Annual Energy Use | 19,600 kWh | 15,800 kWh | 13,800 kWh |
| Annual Energy Cost | $1,170 | $950 | $830 |
| Lifetime Energy Costc | $11,700 | $9,500 | $8,300 |
| Lifetime Energy Cost Savings | — | $2,200 | $3,400 |
a The integrated part-load value (IPLV) corresponds to an average model meeting the minimum national standard EER of 8.9.
b For illustration only, there may not be an actual model available that just meets both EER and IPLV efficiency criteria.
c Lifetime energy cost is the sum of the discounted (present) value of annual energy costs based on average usage and an assumed air conditioner life of 15 years. Future electricity price trends and a discount rate of 3.3% are based on Federal guidelines (effective from April 2001 to March 2002).
Metric Conversions:
1 Ton = 12,000 Btu/h
1,000 Btu/h = 293 watts
°F = (1.8 * °C) + 32
1 Foot = 30.5 cm
Cost-Effectiveness Assumptions: The cost-effectiveness example assumes annual energy use is based on the standard DOE test procedure for a model with 1,500 equivalent full-load hours per year. The assumed electricity price is $0.06/kWh (including demand charges).
Using the Cost-Effectiveness Table: In the example shown above, a commercial unitary air conditioner with an IPLV of 11.0 is cost-effective if its purchase price is no more than $2,200 above the price of the base model. The best available model, with an IPLV of 13.0, is cost-effective if its price is no more than $3,400 above the price of the base model.
Determine Your Own Project's Cost-Effectiveness
Try the Energy Cost Calculator for Commercial Unitary Air Conditioner (Rooftops) to compare the energy costs for your selection with FEMP-recommended and "Best Available" commerical unitary air conditioners. You can model different scenarios by varying electricity cost, capacity, efficiency, and hours of operation.
How to Select Energy-Efficient Commercial Air Conditioners
For contractor-supplied equipment, specify an ENERGY STAR® labeled model or one that meets or exceeds these recommended levels. In early 2002, the Defense Logistics Agency (DLA) expects to offer highly efficient commercial unitary air conditioners with efficiencies that meet or exceed these recommended levels. DLA will select models through a competitive procurement based on lowest life-cycle cost.
Sizing
Oversizing of air conditioners, besides raising purchase cost, will increase energy use, reduce humidity removal, and shorten product life, all due to excessive on-off cycling ("short-cycling"). The required air conditioner capacity should be determined based on the referenced ASHRAE calculation procedure (see For More Information).
Heating Options
Commercial unitary air conditioners can usually be purchased with several options for heating, including a gas or oil furnace, hot water or steam coils, or electric resistance heating. Heat pump models will use less energy than electric resistance heating (see "How to Buy an Energy-Efficient Commercial Heat Pump").
Technology Options
Many factors (not reflected in the efficiency ratings) can affect the energy performance of a commercial unitary air conditioner. Water source models, which use cooling towers, are generally more efficient than air source models, but have higher first costs and maintenance requirements. Economizers provide "free" cooling by using controllable dampers that bring outside air to cool the space when the outdoor temperature or enthalpy are below the building's return air. When properly controlled and maintained, economizers can decrease energy consumption substantially. Two-speed fans allow for decreased energy use in ventilation-only mode, when neither heating nor cooling is needed. Economizers, two-speed fans and other features have impressive energy-saving capability, but usually requires operation by an appropriate and well calibrated control system.
Installation and Maintenance
Proper installation and maintenance of commercial unitary air conditioners are essential for effective and efficient operation. ACEEE's Guide to Energy-Efficient Commercial Equipment, along with other publications from CEE and PNNL, provides tips on installation and maintenance concerns (see For More Information). Duct losses are a major source of energy waste and comfort problems; make sure ducts are well-sealed.
Environmental Tips
Many of today's commercial unitary air conditioners use HCFC refrigerants and other refrigerants with a low Ozone Depletion Factor (ODF). When retiring an air conditioner that contains CFCs or HCFCs, the Clean Air Act requires that the refrigerant be recovered on-site by a certified technician. For information, contact EPA's hotline at (800) 296-1996.
For More Information
- DOE's Federal Energy Management Program (FEMP) Help Desk and World Wide Web site have up-to-date information on energy-efficient Federal procurement, including the latest versions of these recommendations.
Phone: (877) 337-3463. - Environmental Protection Agency maintains a list of compliant models of commercial unitary air conditioners.
Phone: (888) 782-7937 - Consortium for Energy Efficiency (CEE) has utility programs promoting energy-efficient commercial air conditioners and publishes guidelines for good installation practices.
Phone: (617) 589-3949 - American Council for an Energy-Efficient Economy (ACEEE) publishes the Guide to Energy-Efficient Commercial Equipment.
Phone: (202) 429-0063 - American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) publishes the Cooling and Heating Load Calculation Manual.
Phone: (800) 527-4723 - Pacific Northwest National Laboratory (PNNL) supports FEMP's campaign on the procurement of highly efficient unitary air conditioners.
Phone: (503) 417-7558 - Lawrence Berkeley National Laboratory provided supporting analysis for this recommendation.
Phone: (202) 646-7950