A heat pump can save as much as 30% to 40% of the electricity you use for heating.
Why Buy an Energy Efficient Heat Pump?
If you use electricity to heat your home, consider installing an energy-efficient heat pump system. Heat pumps are the most efficient form of electric heating in mild and moderate climates, providing two to three times more heating than the equivalent amount of energy they consume in electricity.
Air source heat pumps are recommended for mild and moderate climate regions, where the winter temperatures usually remain above 30°F. Ground source (also known as geothermal) heat pumps are more efficient and economical to operate when compared to conventional air source heat pumps, especially in climates with similar heating and cooling loads.
Three types of heat pumps are typically available for residences: (1) air-to-air, (2) water source, and (3) ground source. Heat pumps collect heat from the air, water, or ground outside your home and concentrate it for use inside. Heat pumps operate in reverse to cool your home by collecting the heat inside your house and effectively pumping it outside.
Heat pumps have both heating and cooling ratings-both in terms of capacity and efficiency. Capacity ratings are generally in British thermal unit (Btu) per hour or tons (one ton equals 12,000 Btu/hr). Heating efficiency for air source heat pumps is indicated by the heating season performance factor (HSPF). The HSPF tells you the ratio of the seasonal heating output in Btu's divided by the seasonal power consumption in Watt-hours. A heat pump can supply 2 to 3 times as much heat as it consumes in electricity because it moves energy from outside to inside (or vice versa). Heat pump efficiency varies with outdoor temperature. The performance of an air source heat pump in heating mode decreases with the drop in outside air temperature. The actual seasonal efficiency (as opposed to the rating) is therefore higher in a mild climate than in a severe cold climate.
In the cooling mode, a heat pump operates exactly like a central air conditioner. The seasonal energy efficiency ratio (SEER) is analogous to the HSPF but tells you the seasonal cooling performance.
Beginning September 2006, Federal efficiency standards will require that conventional heat pumps have an HSPF rating of at least 7.7 in addition to a SEER rating of at least 13.0. The most efficient air source heat pumps have an HSPF rating between 9.0 and 10.0 and a SEER above 14 or so.
Tips for Buying a New Heat Pump
- Heat pumps must be sized and installed properly to work efficiently. Heat pumps are sized for either the heating demand or cooling demand, depending on which implies the larger unit (almost always cooling). However, heat pumps do not perform well over extended periods of sub-freezing temperature and it may not be cost effective to meet all your heating needs with an air-source heat pump.
- Ground source heat pumps (GSHPs) are more efficient and less noisy than conventional air-source heat pumps. Though GSHPs are more expensive to install, the dramatic improvement in efficiency can yield attractive life cycle cost savings. However, the appropriateness of a GSHP depends on the size of your lot, the conditions of the subsoil and landscape, and sometimes the relative magnitudes of summer cooling and winter heating requirements.
- Select a heat pump with a higher HSPF. For units with comparable HSPF ratings, check their steady-state rating at -8.3°C, the low temperature setting. The unit with the higher rating will be more efficient.
- Select a heat pump with a demand-defrost control. This will minimize the defrost cycles thereby reducing supplementary and heat pump energy use.
- Select a heat pump with an outdoor sound rating of 7.6 bels or lower. The lower the value, the less noisy the outdoor unit.
- If installing a heat pump in an existing home without an existing heat pump or air conditioner, ductwork may need to be enlarged. Heat pump systems generally require larger duct sizes than other central heating systems. For proper heat pump operation, air flow should be 50 to 60 liters per second per kilowatt-hour or 400 to 500 cubic foot per minute per ton of cooling capacity.
- If a heat pump is added to an electric furnace, the heat pump coil can usually be placed on the cold (upstream) side of the furnace for greatest efficiency.
- Fans and compressors make noise. Locate the outdoor unit away from windows and adjacent buildings. Some units also make noise when they vibrate. You can reduce this noise by selecting quiet equipment or by mounting the unit on a noise-absorbing base.
Tips for Lowering Your Heat Pump's Energy Usage
- Do not manually set back a heat pump's thermostat at night. Without a thermostat specifically designed for heat pump set-back, the electric resistance backup heat will engage when the thermostat is raised in the morning, resulting in much higher energy consumption.
- Clean or change filters once a month or as needed, and maintain the system according to manufacturer's instructions. Filter and coil maintenance have a dramatic impact on system performance and service life. Dirty filters, coils, and fans reduce airflow through the system. Reduced airflow decreases system performance and can lead to compressor damage if it continues for an extended period.
- Clean and lubricate the fan motor annually to ensure the required airflow is provided for proper operation. The fan speed should be checked at the same time. Incorrect pulley settings, loose fan belts, or incorrect motor speeds can all contribute to poor performance.
- Outdoor units should be protected from high winds. High winds may reduce efficiency by causing defrost problems. However, outdoor units should not be placed in restricted areas that will result in recirculation of air over the coil.
Source: U. S. Department of Energy