Learn more about the calculator assumptions and definitions.

Assumptions

This energy savings calculator only provides information about the relative difference between two equivalent products, all other factors being equal. Other assumptions include:

This energy savings calculator only provides information about the relative difference between two equivalent products, all other factors being equal. Other assumptions include:

**Base model**- Values represent a 100-ton air-cooled electric chiller operated for 2,000 full-load hours per year with an EER of 9. The performance of this standard unit is based on ASHRAE Standard 90.1.**Default values**- The values pre-loaded into the calculator represent average operating conditions in the Federal sector. Calculations assume that efficiency ratings entered by the user are based on the Air-Conditioning and Refrigeration Institute's (ARI) 1998 Standard 550/590.**FEMP efficiency standard**- Chiller installations are typically optimized for full-load or partial-load operation. FEMP standards mandate that a new product purchase must meet minimum efficiency requirements for both full-load and partial-load design conditions. The energy and cost savings outputs in this calculator are dependent on the primary design condition (either a full-load or a partial-load application), not the combination.**U.S. Federal average electricity price**- $/kWh**Energy efficiency ratio (EER) to kW/ton conversion**- Efficiencies for air-cooled electric chillers are typically measured as EER, whereas water-cooled electric chillers are typically measured in kW/ton. Efficiencies expressed in EER can be converted to kW/ton with the following formula: kW/ton = 12 / EER.**Chiller efficiencies**- In instances where both water-cooled and air-cooled chillers are viable installation options, water-cooled chillers likely offer higher efficiencies at the same capacity when compared to air-cooled chillers.-
**Calculator constants****Uniform present value (UPV)**– 16.34**Lifetime energy costs**- Values represent the sum of the discounted value of annual energy costs, based on an assumed chiller life of 23 years.**Price trends and discount rate**- Future electricity price trends and a discount rate of 3% are based on Federal guidelines.

**Energy efficiency ratio (EER)**is the ratio of net cooling capacity (or heat removed in Btu/h) to the total input rate of electric power applied in watts. The units of EER are Btu/Wh. A higher EER value indicates a more efficient system.**Uniform present value (UPV)**is a discount factor calculated from the NIST product lifetime and utility rate.**Integrated part-load value (IPLV)**is an efficiency metric calculated using AHRI Standard 550/590 test conditions at load capacities of 25%, 50%, 75%, and 100%. It is intended to provide comparative information about a chiller used under variable load conditions.

Note: Full-load and IPLV efficiencies are derived from standard test inputs and are therefore generically comparable. NPLV must be calculated for the specific load rating points desired for each chiller being compared.