The amount of dishes to be washed will be the major factor in determining the type of dishwasher to purchase. When you look at machine capacities you first need to understand and decode the manufacturer's ratings. Most manufacturers advertise the capacity of their machines by the number of racks per hour it can handle based on their NSF (National Sanitation Foundation) listing. While the ratings are not meant to deceive, do not be fooled by these theoretical capacities. The ratings for door type machines that are typically about 40 - 60 racks per hour and start at 200 racks per hour for conveyor machines can be misleading. These numbers are computed mathematically and are not based on actual machine operation that must allow for loading and unloading the machine.

A typical rule of thumb is that the actual production of a machine in racks per hour is about 70% of the manufacturer's rating. In other words, if a machine is rated at 200 racks per hour you should expect to be able to wash about 140 racks per hour assuming you have a constant volume of dishes to be washed. The same is true for manufacturers' claimed capacity of dishes per hour. The actual dishes per hour may be even less than 70 percent since the claims are usually based on a relatively small dish or glass size that fits a 20" × 20" rack optimally.

Once the size and style of machine has been determined, there are several other initial purchase decisions to make. Energy efficiency needs to be considered. As if it isn't enough that dishwashers are very expensive and take up a lot of floor area, they are also energy hogs. Dishwashers are typically the single biggest energy and water user in a restaurant.

A standard dishwasher uses super heated 180° F water to sanitize dishware. There are also low temperature or chemical sanitizer machines that use chemicals to sanitize dishware. These machines are not for all operations. A benefit of the high temperature final rinse is quick drying of dishware and low energy consumption. High temperature machines are also better able to break down animal fats and grease as well as lipstick on glassware and dishes. Most chemical sanitizing machines use sodium hypochlorite (bleach), in lieu of 180° F water to chemically sanitize items being washed in the machine. It is critical to note that certain materials, including silver, aluminum, and pewter, are attacked by bleach and cannot be washed in a machine set up for chemical sanitizing.

Reduced energy and water consumption is important to everyone. Manufacturers have developed some substantial new technology to cut energy and water usage. One of the biggest introductions is new final rinse nozzles that create a spray pattern that provides dish coverage using less water. Other new provisions like insulated wash and rinse tanks are becoming more popular as energy prices soar.

For more on energy consumption, you can look at the Energy Star web site.

Dan Bendall is a principal of FoodStrategy, a Maryland-based consulting firm that specializes in planning foodservice facilities. A member of Foodservice Consultants Society International (FCSI), Bendall can be reached at 240-314-0660.