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Warewashing Equipment – Commercial Dishwashers and Pre-Rinse Spray Valves

How Much Will I Save?

The following examples provide hypothetical energy and/or water savings totals associated with the use of high-efficiency commercial dishwashers or pre-rinse spray valves.  It should be noted that the annual cost savings and payback periods are illustrative, and will depend on your actual energy, water, and equipment costs.

For commercial dishwashers and pre-rinse spray valves, energy savings is realized through lower water use.  In Canadian commercial accommodation and food service establishments, the percentages of gas, electric, and oil water heating are 77 percent, 6 percent, and 17 percent, respectively.1 In calculating potential energy savings for these products, the following assumptions are used:

Assumptions
Efficiency of a gas water heater2  70 %
Efficiency of an electric water heater3  95 %
Efficiency of an oil water heater  80 %
Water heater energy output 143,000 J per litre

Example of Energy and Water Savings Potential of
a High-Efficiency Door Type High-Temp Commercial Dishwasher

On average, a door type high-temp dishwasher cleans 300 racks of dishes per day for 360 days per year, resulting in an annual total of 108,000 racks cleaned.   If a baseline dishwasher with a rinse water consumption of 15.1 litres/rack (4.0 gallons/rack) is replaced with a high-efficiency dishwasher with a rinse water consumption of 3.6 litres/rack (0.95 gallons/rack), the annual cost savings will be at least $5,160 and the maximum payback period of the investment will be less than 8 months.

Annual
Estimates
per
Dishwasher
Water
Consumption
(L per year
per
Dishwasher)
Energy Consumption
Natural Gas
(MJ per year
per
Dishwasher)
Electricity
(kWh per year
per
Dishwasher)
Oil
(MJ per year
per
Dishwasher)
Baseline 1,630,800 333,149 68,188 291,506
High-Efficiency   388,800   79,426 16,257   69,498
Savings 1,242,000 253,723 51,931 222,008
Water or
Energy Cost
$1.59/m3* $0.48/m3 $0.10/kWh $0.89/litre
Cost Savings $1,975 $3,188 $5,193 $5,064
Total Cost Savings $5,160 $7,170 $7,040
Estimated Equipment
Cost Differential
$3,320 $3,320 $3,320
Payback Period 7.7 months 5.6 months 5.7 months

* Includes both water and sewer costs

Example of Energy and Water Savings Potential of a Low-Flow PRSV

On average, a PRSV is used for 1.27 hours per day for 360 days per year, resulting in an annual total use of 457.2 hours. If a baseline PRSV (12.9 Lpm (3.4 gpm)) is replaced with a low-flow PRSV (6.1 Lpm (1.6 gpm)), the annual cost savings will be at least $775 and the payback period of the investment will be less than one month.

Annual
Estimates
per
PRSV
Water
Consumption
(L per year
per
PRSV)
Energy Consumption
Natural Gas
(MJ per year
per

PRSV)
Electricity
(kWh per year
per
PRSV)
Oil
(MJ per year
per

PRSV)
Baseline 354,000 72,291 14,796 63,255
Low-Flow 167,000 34,184 6,997 29,911
Savings 187,000 38,107 7,800 33,344
Water or
Energy Cost
$1.59/m3* $0.48/m3 $0.1/kWh $0.89/litre
Cost Savings $297 $479 $780 $761
Total Cost Savings $775 $1077 $1057
Estimated Equipment Cost $50 $50 $50
Payback Period 3.4 weeks 2.4 weeks 2.5 weeks

* Includes both water and sewer costs.

An annual water and energy cost calculator for pre-rinse spray valves may be found at the Food Service Technology Center website. It should be noted that costs should be entered in Canadian dollars, as the defaults are based on U.S. dollar costs.

1 Comprehensive Energy Use Database Tables, Table 75: Accommodation and Food Services Non-Space Conditioning Secondary Energy Use by End-Use and by Energy Source.  Available on the NRCan website.
2Program Guidance on Pre-Rinse Spray Valves,” published as a part of the Consortium for Energy Efficiency's Commercial Kitchen Initiative.
3 “Good to the Last Drop: Proven Opportunities for Commercial and Institutional Water Conservation”, PNWS/AWAA Water Conservation Committee, February 2006.