Glossary of Energy Terminology

We understand energy related terms can be complicated and hard to understand. To help here is a glossary of frequently used terms.

Heating, Ventilation and Cooling Terminology

Btu: Btu, which stands for British Thermal Unit, is a measurement of heat energy. One Btu is the amount of heat required to raise the temperature of one pound of water by 1°F. For example, the heat produced by burning one wooden kitchen match is the equivalent of one Btu.
Heat Pump: A heat pump is like an air conditioner with a reversible valve, which allows it to operate in reverse, taking heat from your house and pushing it outdoors in the summer, and pulling heat from outdoor air and bringing it back into your house in the winter. Heat pumps are more efficient than other forms of heating because they do not actually create heat; they just move it from one location to another.
EER: The instantaneous measurement of the cooling efficiency of your air conditioner or heat pump is known as its Energy Efficiency Ratio or EER. An air conditioner or heat pump with a high EER means that it's very efficient.
Insulation: Insulation is material that resists the transfer of heat, usually by incorporating small pockets of air. The way to rate insulation is in terms of thermal resistance, called R-value, which shows the resistance to heat flow. If the R-value is high, then the insulating effectiveness is high as well. The R-value of thermal insulation depends on the type of material, as well as its density and thickness.

Frame material: Vinyl, fiberglass, or wood frames conduct less heat than aluminum frames, which makes these windows much more efficient.
Thermal break: Putting a substance that does not transmit heat well, like plastic, inside the metal parts of the frame reduces the heat being transferred through the frame. Thermal breaks can be used in the main body of the window frame or they can be used in multi-pane windows as part of the spacer between panes of glass.
U-Value: U-Value is a measurement of heat flow. The slower the window transfers heat in and out of a house, the lower the U-value.
R-Value: R-value is a way to measure heat resistance. The higher the R-value of a house, the better the window resists the transfer of heat; this is the inverse of the U-value.

Peak-hour demand: The maximum water usage allowed, in gallons per hour, during the time of day when your family will most likely use the most hot water.
Energy Factor: Energy Factor (EF) measures the efficiency of a water heaters' storage, which is based off an average hot water usage of 64 gallons per day. The more efficient the water heater is, the higher the EF.
Water Heater Temperature: The temperature of your water heater is controlled by a thermostat. Money can be saved by lowering the temperature of the water heater to 120°F (about midway between the "Low" and "Medium" settings). If your dishwasher doesn't have a heating element, leave your thermostat on the "Medium" setting (140°F).

Lumen: The total amount of light given off from a source is called a lumen. Lumens are used to measure or rate the output of lamps.
Lamp: The term lamp is used to refer to the source of light, or the light bulb itself, not the fixture that contains the light bulb.
Incandescent lamp: This refers to the glass bulbs with a filament inside, or the most common source of light. Around ninety percent of the energy used by an incandescent lamp is given off as heat and not light.
Compact Fluorescent: This lamp can replace standard incandescent lights and it is a smaller, more compact version. Contained within the light is a gas-filled tube and a electronic or magnetic ballast. Compact Fluorescent Light Bulbs (CFLs) contain small amounts of mercury, please dispose of properly.

Didn't find what you were looking for? Click here to visit the Department of Energy website for a complete list of energy related terms.