It often pays to read the compressor control instructions!
One compressed air system owner had two 150-hp load/unload compressors operating at the plant. A survey of the compressor hours showed that both compressors were running for significant periods of time in the unloaded condition, still consuming 40 kW, but producing no air.
A compressed air auditor was consulting and monitored the system with data loggers. The readings showed that the compressors were not set to shut off when running unloaded for an extended period of time. This setting is called auto restart on this particular brand of compressors.
When the compressors were commissioned, nobody thought to read the manual and turn auto restart on. Running in the unloaded condition not only wastes energy — in this case $24,000 per year — but it also causes the compressor to require more maintenance, wasting even more money.
It pays to read the manual and enable any efficiency features on your compressors, where appropriate!