System Capacity
System capacity is a measurement of the total amount of heat or cooling your furnace, heat pump or air conditioner can produce in one hour. This amount is reported in Btu/hr on the nameplate of your equipment. |
Btu
Btu, short for British Thermal Unit is a unit of heat energy. One Btu is the amount of heat needed to raise the temperature of one pound of water 1°F. To get a rough idea of how much heat energy this is, the heat given off by burning one wooden kitchen match is approximately one Btu.
AFUE
The AFUE, or Annualized Fuel Utilization Efficiency, is the ratio of the total useful heat your gas furnace delivers to your house to the heat value of the fuel it consumes.
Heat Pump
A heat pump is basically an air conditioner with a reversible valve that allows it to operate in reverse, removing heat from your house and shunting it outdoors in the summer, and removing heat from outdoor air and shunting it into your house in the winter. Because heat pumps do not actually create heat-they just move it from one place to another-heat pumps are more efficient than other forms of heating.
COP
Coefficient of Performance, COP, is the ratio of energy input to heating capacity. This is the instantaneous measurement of the heating performance of your heat pump. It is comparable to knowing how many miles per gallon of gasoline your car gets when it is going full speed. You can find the COP on the nameplate of your heat pump.
HSPF
The Heating Seasonal Performance Factor, HSPF, is an efficiency rating for heat pumps. It is a measure of the average number of Btu of heat delivered for every Watt-hour of electricity used by the heat pump over the heating season. It takes into account variations due to weather conditions over a season. HSPF is comparable to knowing how many miles per gallon of gasoline your car got, averaged over the entire year.
EER
Energy Efficiency Ratio, EER, is the instantaneous measurement of the cooling efficiency of your air conditioner or heat pump. The higher the EER for your air conditioner or heat pump, the more efficient it is.
SEER
The Seasonal Energy Efficiency Ratio, SEER, measures the average cooling efficiency, over the entire cooling season for your air conditioner or heat pump.
Programmable Thermostat
A thermostat with the ability to record different temperature settings for different times for your heating and/or cooling equipment. Programmable thermostats can be electronic, or mechanical.
ACH
ACH stands for Air Changes per Hour. It is the number of times in one hour that the air in your house is completely replaced with outside air.
Conduction
The transfer of heat through a solid material.
Convection
The transfer of heat by air flow.
Radiation
The transfer of heat directly from one surface to another (without the intermediate air acting as a transfer mechanism).
