One of the important total operating cost decisions made by the management of an industrial plant is how much money to spend for scheduled electrical preventive maintenance. The amount of maintenance of a component can affect its failure rate. Very little quantitative data have been collected and published on this subject. There is an optimum amount of scheduled electrical preventive maintenance that minimizes the total of the maintenance costs plus the costs associated with failures and power outages. Reliability surveys conducted by the IEEE Industry Applications Society Power Systems Reliability Subcommittee during 1973-1980 have shown that inadequate maintenance is a significant cause of electrical equipment failures in industrial plants. A summary of this IEEE data for several categories of electrical equipment is given. Also included is a summary of a recently published paper on this subject where an optimum maintenance interval has been determined for 23 categories of electrical equipment.