If the dishwasher in your restaurant is more than 10 years old, you are almost certainly wasting money in energy usage. On the other hand, the most recent generation of dishwashers offers real improvements in energy and water savings. Here are the features to look for and where some of those savings are.

Aside from high energy costs, the equipment’s initial expense is often the highest of any item in your kitchen. You’ll spend more than $10,000 for even a small single-rack machine. So let’s be sure you get your money’s worth when you buy.

One of these smaller machines can serve a restaurant with up to 120 seats. If your place has more than 130 seats, you’ll need a rack conveyor machine. This type may cost $20,000 or more depending on size, number of tanks and accessories. After you add in a clean dish table, soiled dish table, final rinse booster heater and a few dish dollies and racks, it’s not uncommon to spend $50,000 or more on a conveyor machine. It will pay to have a basic understanding of what is available on the market.

There are three basic types of dishwashers that are typically used in restaurant operations. Very small operations may be able to use an undercounter machine that has a realistic washing capacity of about 40 to 50 full place settings per hour. These are primarily suited to a very small operation or snack bar.  

Do not try to use a residential dishwasher in your commercial operation because it will not meet the strict sanitation code requirements. If you use a commercial undercounter machine, remember that most local health departments require separate clean and soiled dish drain boards, separated to prevent cross contamination.  

The next step up in dishwasher size is the door-type or full-height single rack machine. This machine type washes and rinses a rack of dishes in a little over a minute and can process about 90 to 110 place settings per hour. It’s suitable for a small- to medium- size restaurant.

The typical door-type machine fits in a footprint about 24 inches square and delivers a tremendous amount of washing power using recirculated water.  

The machines being made today also conserve water, often using only less than a gallon of fresh water per cycle. Most manufacturers make their door-type units in a straight or corner configuration.  

Rack conveyor machines have the ability to clean up to several hundred place settings per hour. Their lengths range in size from 44 inches to about 10 feet. All machines start with a basic wash tank and then add other modules that may be beneficial. For example, some models have one or two different prewash modules that are very effective for scrapping and removing heavy soil from dishware. A prewash unit will cost you an additional $6,000.

If you want to take the next step up to higher capacity and better performance, then the addition of a rinse tank or an extended wash tank is necessary.

Generally, the conveyor and single rack models require an exhaust hood to vent steam and heat. However, a few manufacturers now have a feature that condenses and extracts the steam to preheat its own water. No exhaust hood is required, which will save you heating and air-conditioning (HVAC) costs and the cost of installing a hood and ductwork.

You may also want to look at other units that can now extract waste heat from hot water going down the drain to preheat water for future washes. 

Knowing your operation's needs

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Flight-type machines are a fourth dishwasher style, but they are generally used in institutions and extremely high volume operations for mass feeding.  

Using low-temperature or chemical sanitizer machines is one way to save on hot water costs and reduce some ventilation requirements. These machines are sometimes mislabeled as cold water machines, but all dishwashers must use hot water. The low-temperature machines just don’t use the super hot 180° rinse water.  Instead, they use a sanitizing chemical in the final rinse to do the job.

As an operator you must weigh the cost of the sanitizing agent against the energy savings. Also, be aware that a benefit of a high-temperature final rinse is a dishware that dries quickly. High-temperature machines are also better able to break down animal fats and grease as well as lipstick on glassware and dishes.    

In recent years, several manufacturers have developed machines that reduce water consumption by 30 to 60 percent over older similar sized machines. Except for the initial filling of the wash tanks at the beginning of the shift, the only fresh water used in dishwashers is in the final rinse.

One way these machines save water is with a simple innovation of changing the size of the water droplets in the final rinse portion of the wash. It was found that using a different size water droplet significantly increased the heat transfer to dishware, aiding in sanitation and reduced water consumption. The droplet size and scientifically designed spray patterns have been the cornerstones to reducing typical booster heater sizes by almost half in many cases.  

The booster heater is used to heat water from 140° to a sanitizing temperature of 180°.  Cutting booster heater size is huge since the electrical loads on many older machines are 50 kilowatts or more. Reducing that load to 30 kilowatts or less yields a significant cost savings.

Knowing your operation’s needs and what is available on the market will help you choose the right capacity dishwasher for your operation. Be sure to ask and compare energy and water usage, not just initial cost of the equipment. Look for the water and energy saving features mentioned here. Then, when you get your new machine, take care of it. Perform regular preventive maintenance, including deliming.  

Dan Bendall is a principal of FoodStrategy, a firm specializing in planning foodservice facilities.