This paper is based on data gathered from actual service records of heat pumps under service contract with a major electric utility company. The maintenance contract program was started in 1967 and has operated for 20 years. Records are kept on each service call during the contract period, which extends from the first through the tenth year of operation.

Major conclusions include:

1. Heat pump reliability has improved dramatically in the past 20 years.
2. Compressor failure rates are at record low levels.
3. The cost per service call reflects a significant expenditure to the homeowner.
4. The ratio of necessary service calls per year to units installed has improved to 1:5.2 from 1:1.4 10 years ago.
5. The cost of maintenance for a heat pump in 1987 is less than half of what it was 10 years ago.