Manufacturers and retailers offer a wide array of heat pumps, and heat-pump selection is a unique process that each homeowner must carefully consider. Choosing these devices--which move heat from an outside heating element to the inside of a home--requires a considerable amount of research involving the home's structure and materials. With some basic knowledge and research, though, homeowners can select the appropriate heat-pump size with only minimal hassle.

Climate

Heat pump selection depends on a number of factors, and the outside climate can be one of the greatest considerations in the selection process. Very cold climates require heat pumps to work harder and more frequently, making larger heat pumps more appropriate because they can pump a greater volume of hot air into the home. AC Direct, a heat pump retailer, recommends becoming familiar with the average wintertime low temperatures before shopping for a heat pump. To help with this process, consider using free online weather research resources such weather.com or infoplease.com. Because climates vary considerably from area to area, no standard formula exists to support selection of a heat pump based on a home's size. A home in Florida, where winter low temperatures rarely fall below 40 degrees, may require a smaller heat pump than a similar home in Michigan, an area where winter lows dip to the single digits.

Heat Loss

Second to the home's general environment, the rate at which a home loses heat is a primary factor in heat-pump selection. A number of factors---ranging from the amount of insulation in the home to the number and size of windows, and even the types of materials used in the home's construction--contribute to a home's heat loss. Heat pump vendors at Leonardo Energy suggest having the home's heat loss evaluated by qualified specialists. Although newer homes tend to be somewhat better insulated than older homes, no concrete rules exist to quickly and easily determine how quickly a home loses heat. At least one online calculator offers homeowners the ability to calculate a home's heat loss. However, AC Direct, the company that offers the calculator, warns that the process requires considerable research on dimensional and construction details of the home.

Capacity and Efficiency

After verifying local climate information and researching the home's heat loss, a homeowner must carefully consider a heat pump's capacity while selecting a unit. Heat pump manufacturers may describe the device's output capacity in measures of kW or in an older, more widely recognized measure expressed as British Thermal Units (BTUs). For efficiency purposes, the United States Department of Energy also provides a calculation known as the Coefficient of Performance--expressed as BTU/h--that indicates the unit's energy efficiency. All of these factors play vital roles in selecting an appropriately sized heat pump. A unit that is too large may frequently cycle on and off, a process known as short cycling, or improperly remove humidity from the home's air. For the most accurate assessment and heat pump selection, consider contacting a professional heating, ventilation and air conditioning (HVAC) professional for assistance after researching the home's structure and the local climate.

Source:

AC Direct: Sizing Heat Pumps

Leonardo Energy: What Size Heat Pump Do I Need?

US Department of Energy: How to Buy an Energy-Efficient Commercial Heat Pump

Resource:

Weather.com Climate Research Tool

InfoPlease Climate Research Tool