Energy efficiency for most warewashers begins with the reduction of the amount of water that is used.
Reducing water consumption reduces costs and is the greatest energy savings available for warewashers. Ten years ago, a typical flight-type dishwasher used 300 gallons per hour of final rinse water, but today there are flight-type machines with a similar throughput that use as little as 60 to 90 gallons of water per hour.
Waste heat recovery systems can further reduce energy consumption by using heat that is typically vented out of the building to preheat cold water being fed to the machine. Typically, this eliminates the need to draw hot water from the building's hot water heater, except for a one-time fill at the beginning of the shift, reducing energy costs. It also cools the exhaust air.
Some manufacturers offer built-in filtration systems ranging from a passive filter that the wash water must pass through as it is pumped, to small active pumps that work in conjunction with filters to strip soil out of the water. Typically, both systems redirect the soil to the drain line, which also eases cleaning, reducing labor costs.
Most rack conveyor and flight-type conveyor dishwashers use a cascading water system, where the final rinse water is captured, and then flows into the wash tank, then into the prewash tank, and finally down the drain. Diverting a portion of this nearly-clean water directly to the prewash forces soiled water out of the machine early. This reduces the overall level of soil in the machine and the need for detergent.