Poor installation, duct losses, and inadequate maintenance are more of a problem for heat pumps than for combustion furnaces. A growing body of evidence suggests that most heat pumps have significant installation or service problems that reduce performance and efficiency.

According to a report on research funded by Energy Star‚ more than 50 percent of all heat pumps have significant problems with low airflow, leaky ducts, and incorrect refrigerant charge. You may be able to improve the performance of your system by increasing airflow, sealing ducts, or adjusting the refrigerant charge.

The capacity and the efficiency of a central heat pump depends upon adequate airflow. There should be about 400 to 500 cubic feet per minute (cfm) airflow for each ton of the heat pump's air-conditioning capacity. Efficiency and performance deteriorate if airflow is much less than 350 cfm per ton.

An ideal duct system has both a supply register and a return register for every room. Most homes, however, have only one or two return registers for the entire house. Air from other rooms must find its way back to these registers to be reheated or re-cooled. Obstructions in return air are a common air circulation problem, particularly from closed interior doors to rooms with no return-air register.

Blockage of supply or return air ducts and registers can pressurize or depressurize portions of the home, resulting in poor performance and increased air leakage through the building envelope. Restrictions to airflow have the greatest impact on the return-air side of the system, so repairs should start with the return ducts.

Air from every supply register must have an unobstructed pathway back to a return register. You can install louvered grilles through walls or doors, ducts between rooms, and/or additional return ducts and registers to improve air circulation.

Technicians can increase the airflow by cleaning the evaporator coil, increasing fan speed, or enlarging the ducts —- especially return ducts. Enlarging ducts may seem drastic but in some cases, might be the only remedy for poor comfort and high energy costs.