Let’s first look at the EER, or Energy Efficiency Ratio, definition: It is the measure of the relative, but not overall, efficiency of a cooling or heating appliance or equipment. It is expressed as the ratio of output in British thermal units (BTUs) per hour to the energy consumed in watts.

To find the Energy Efficiency Ratio (EER) of a single cooling device you take the ratio of output cooling energy in BTU, to input electrical energy in Wh—at a given operating point. You usually calculate EER using a 95°F or 35°C outside temperature and an inside temperature, which is returned air, of 80°F or 26.7°C with 50% relative humidity.

When buying an air conditioner look for EER ratings higher than 10 as these are considered the most cost effective. The higher the ratio, the less the unit will cost you to operate. Therefore, to reduce your energy bills look for a high EER rating and EnergyStar® compliance.

SEER definition: It is a measure of cooling efficiency for air conditioning products. Just like EER, the higher the SEER rating the more energy efficient your appliances or equipment.

SEER (Seasonal Energy Efficiency Ratio) is related to COP (Coefficient of Performance), the difference between the two is that the COP of a cooling device is unit-less because the numerator and denominator are expressed in the same units, while the SEER of a cooling device is a mix of units.

When you rate a unit using SEER, you take the cooling output during a typical cooling season and you divide that by the total electric energy input during the same period. Obviously, the higher the SEER rating, the more energy efficient the unit is. If you live in the U.S., it’s a little different. The SEER is the ratio of cooling in BTU to the energy consumed in watt hours.

Using mixed units, you obtain the SEER by multiplying the COP or EER by the conversion factor from BTU/h to watts.

The definition of COP is the ratio of work or useful output to the amount of work or energy input. Usually, like EER and SEER, it is used as a measure of the energy efficiency of cooling and heating appliances or equipment.

When buying new appliances or equipment, check the EER or SEER. With EER you will know how well a room air-conditioner operates based on the power it uses, and with SEER you will know how well the central air conditioner operates across an entire season.

Save money with higher EER or SEER ratings. Especially if you are a business owner. These higher ratings can translate into huge savings as businesses run appliances and equipment round the clock. Think about this: Buying a piece of equipment for your business with a higher rating, even if it costs you more, will generate huge savings not over the long term, but over the short term.