Saving Energy with a Heat Pump

When purchasing a new heat pump, be sure to check the efficiency rating of the proposed unit. A higher efficiency rating will result in lower operating costs. Heat Pump efficiency is designated by the term "SEER" (Seasonal Energy Efficiency Ratio). New units have SEERs ranging from 10.0 to over 16.0.

For split systems with an outdoor unit and an indoor coil, the efficiency varies with the match between the indoor cooling coil and outdoor condensing unit. The manufacturer should be consulted to determine the combined efficiency. The American Refrigeration Institute (ARI) publishes an annual directory listing various combinations of outdoor units and indoor coils with their SEER rating. Most major manufacturers' product lines are included in this directory.

Over the past several years, the SEER for the highest efficiency heat pumps has increased from 12.0 to over 16.0 due to the incorporation of the following improvements:

• Variable speed blowers, compressors, and motors - This equipment provides variable speeds of operation to optimize performance and efficiency. Heat pumps utilizing multi-speed components will typically start in the first stage or low speed. If comfort levels or control settings cannot be satisfied with the first stage, the second stage or high speed will activate. Some heat pump systems have more than two stages or speeds of operation.
• Larger Coil Surface Areas - Large surface coils provide maximum heat transfer efficiency.
• Time Delays - Time delays vary the on and off cycles of compressors, motors, and supplemental heat packages.
• Expansion Valves - Expansion valves control the flow of refrigerant in proportion to the load on the evaporator. Compared with other types of fixed metering devices, expansion valves are able to exercise control over a much wider range of operating conditions.

Other Energy-Efficiency Features

Besides a unit's SEER, there are additional energy saving features to look for when selecting a heat pump for your home.

• Dual fuel back-up- Dual fuel heat pump systems are supplemented by a fossil fuel furnace or boiler instead of the traditional electric resistance coils. When outdoor temperatures are moderate, the building heat requirements can be satisfied by the heat pump alone. When outdoor temperatures are below the economic balance point, the heat pump is switched off and the furnace or boiler supplies heat at close to its peak efficiency.
• Programmable setback thermostats - Programmable thermostats with adaptive-recovery or "ramping" are designed specifically for use with heat pumps. They allow the thermostat to be programmed for one or more "setback" periods per day. Their microprocessor unit senses the temperature differential to be overcome when bringing the space temperature back up, and brings the temperature up gradually over a longer period of time. This allows the heat pump alone to provide the temperature increase and minimizes the use of electric resistance auxiliary heat.

Operation & Maintenance

The following are some guidelines that should be followed to ensure efficient, comfortable operation of heat pumps.

• In the heating mode, do not set the temperature back at night or when you are at work unless a programmable heat pump thermostat is used. Since heat pumps operate differently than fossil fuel heating systems, setback of a standard heat pump thermostat can actually increase energy consumption. This is due to the use of supplemental heaters to bring the house temperature back to the desired setpoint. Use of supplemental heaters will reduce the efficiency of the heat pump system and result in higher energy costs.
• Keep the temperature setpoint consistent. A standard heat pump thermostat has two controls, one for the heat pump and one for the supplemental heat. If the temperature difference between the room and thermostat setpoint is more than 2° or 3° F, the supplemental heat will be activated. Manually adjusting the thermostat will result in greater reliance on the supplemental heaters and will reduce the efficiency of the heat pump system and increase operating costs.
• Replace filters regularly. Vacuum dirt and dust from the indoor coil once a year to prevent restricted airflow. Adequate air flow through a heat pump system is critical to ensure efficient and comfortable operation.
• Keep supply vents open and free from obstruction. Closing off supply vents will restrict air flow and reduce system efficiency as well as reduce the life of the compressor.