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Energy Efficient Air Conditioner Terms

At John C. Flood we often get asked what certain HVAC industry terms mean, so below we offer some common questions along with answers to help you better understand HVAC terms.

What size air conditioner do I need for my house?

Sizing a residential heating, ventilating and air conditioning (HVAC) unit depends on such variables as square footage of your home, geographic location, orientation to the sun, construction details, insulation values, window area and type, etc. Under sizing a system may lead to warmer or cooler temperatures than desired by some occupants. Over sizing the system may lead to humidity or moisture control problems in the space.

What is a BTU?

BTU stands for the British Thermal Unit (Btu). It's a unit of heat energy within the inch-pound unit system, which is common today in the United States. The Btu is defined as the amount of heat necessary to raise the temperature of one pound of water one degree Fahrenheit from 58.5 to 59.5.

A Btu is commonly used to indicate the heating and cooling capacity of a system, heat losses, and heat gains. To give an example of system capacity, a 10,000 Btu window air conditioner is capable of removing 10,000 Btus of heat per hour. To give an example in terms of heat gains, the typical heat gain added to a room by a person at rest is about 230 Btu per hour.

What is a Ton?

A ton is the unit of measurement for air-conditioning system capacity. One ton of air conditioning removes 12,000 Btus of heat energy per hour from a home. Central air conditioners are sized in tons. Residential units usually range from 1 to 5 tons.

What does EER mean? Should I spend more money for a higher EER unit?

EER stands for energy efficiency ratio. The higher the EER rating, the more energy efficient the equipment is. This can result in lower energy costs. If you go to the US Dept of Energy's Web site you can calculate the potential energy cost savings of a more efficient unit. The Air-Conditioning and Refrigeration Institute (ARI.org) posts a Certified Ratings directory, which lists EER ratings of various air- conditioning equipment.

What does SEER mean? Should I spend more money for a higher SEER unit?

SEER stands for seasonal energy efficiency ratio. The higher the SEER rating, the more energy efficient the equipment is. A higher SEER can result in lower energy costs. Again, if you visit the U.S. Dept. of Energy's Web site you can calculate potential energy cost savings of a more efficient unit. Once more the Air-Conditioning and Refrigeration Institute (ARI.org) posts a Certified Ratings directory, which lists SEER ratings of various air-conditioning equipment.

What does HSPF mean?

HSPF stands for heating system performance factor. The higher the HSPF rating, the more energy efficient the equipment is. A higher HSPF can result in lower energy costs. The Air-Conditioning and Refrigeration Institute (ARI.org) posts a certified ratings directory, which lists HSPF ratings of various air-conditioning equipment.

What does AFUE mean?

AFUE stands for annual fuel utilization efficiency. The higher the AFUE rating, the more energy efficient the equipment is. A higher AFUE can result in lower energy costs. The Gas Appliance Manufacturers Association at www.gamanet.org, publishes a directory of certified AFUE ratings.