In the United States, the efficiency of air conditioners is often rated by the seasonal energy efficiency ratio (SEER) which is defined by the Air Conditioning, Heating, and Refrigeration Institute, a trade association, in its 2008 standard AHRI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.
The SEER rating of a unit is the cooling output during a typical cooling-season divided by the total electric energy input during the same period.
In the U.S., the SEER is the ratio of cooling in British thermal units (BTUs) to the energy consumed in watt-hours.
The seasonal energy efficiency ratio (SEER) is also the COP (or EER) expressed in BTU/watt-hour, but instead of being evaluated at a single operating condition, it represents the expected overall performance for a typical year's weather in a given location.
There is no allowance for different climates in this rating, which is intended to give an indication of how the EER is affected by a range of outside temperatures over the course of a cooling season.
The maximum EER decreases as the difference between the inside and outside air temperature increases, and vice versa.
For example, there is little cost benefit in having a very high SEER air conditioning unit in Maine, a state in the northeast US.
Starting January 1, 2015, split-system central air conditioners installed in the Southeastern Region of the United States of America must be at least 14 SEER.
Similarly, split-system central air conditioners installed in the Southwestern Region must be a minimum 14 SEER and 12.2 EER beginning on January 1, 2015.
Split-system central air conditioners installed in all other states outside the Southeastern and Southwestern regions must continue to be a minimum of 13 SEER, which is the current national requirement.
[6] There have been many new advances in efficient technology over the past 10 years which have enabled manufacturers to increase their SEER ratings dramatically in order to stay above the required minimums set by the United States department of energy.
The annual cost of electric energy consumed by an air conditioner may be calculated as follows: Example 1: An air-conditioning unit rated at 72,000 BTU/h (21 kW) (6 tons), with a SEER rating of 10, operates 1000 hours per year at an electric energy cost of $0.12 per kilowatt-hour (kW·h).
First, we convert tons of cooling to BTU/h: The annual cost of the electric energy is: Today there are mini-split (ductless) air conditioner units available with SEER ratings up to 42.
[10][11] During the 2014 AHR Expo, Mitsubishi unveiled a new mini-split ductless AC unit with a SEER rating of 30.5.
[13] Carrier launched a 42 SEER ductless air conditioner during 2018 Consumer electronic Show (CES), held in Las Vegas.
Also, practically, central systems will have an achieved energy efficiency ratio 10–20% lower than the nameplate rating due to the duct-related losses.
[15] However, ground-source heat pump effective efficiency is reliant on the temperature of the ground or water source used.
Moreover, the ARI rating scheme for ground-source heat pumps allows them to largely ignore required pump power in their ratings, making the achievable SEER values often practically lower than the highest efficiency air-source equipment—particularly for air cooling.
[16] Some of these technologies include rotary compressors, inverters, DC brushless motors, variable-speed drives, and integrated systems such as those found in solar-powered air conditioning.
An ideal resistance heater converting 100% of its input electricity to output heat would have COP = 1, equivalent to a 3.4 EER.