Editor's note:The Energy Services Bulletin features real answers to real questions posed to our staff at the Energy Services Power Line. We hope you find it useful.

Question:

Would heat-pump water heating be a cost-effective alternative to a conventional electric water heating system for a small restaurant?

Answer:

There are several options you should look at with regard to heat-pump water heaters in a restaurant setting. The following options range from simple to complex:

1. Replace electric hot water with HPWH — There are direct HPWH replacements available for electric hot water. These range in cost depending on the size and options. A rough savings estimate of 50 percent is reasonable, but depends on the model. For a restaurant, larger hot water storage is recommended since heat pumps do not recover as quickly as electric elements. The byproduct of heating the water is cold air. This could be used to help cool the kitchen area.

2. Add a heat recovery unit to the existing air conditioning — The air-conditioning system could have a heat reclaim unit added that will supplement the hot water system. The waste heat from the air-conditioning unit pre-heats water used in the electric system. This option only provides benefit during the summer.

Replace the electric water heater and air-conditioning — Heat pump units that heat hot water and cool the space are also available. During the winter, the unit only heats water.

Add heat-reclaim units to the dishwasher drain — Heat reclaimed from the dishwasher can be used to preheat water to the hot water tank with either system.

Resources to help with your decision

Obviously, each system comes with a price. Several resources may be helpful in making your decision.

• Residential Heat Pump Water Heaters from the Federal Energy Management Program is the first and best resource. It has a good overview of residential HPWH and includes methods for calculating energy savings which can be modified easily for commercial use. It also includes costs of various systems, but these are several years old.

• The fact sheet Energy-efficient water heating: Purchasing a new electric water heater, Western Area Power Administration. This covers HPWH generally, along with other technologies.

• Heat Pump Water Heaters—Residential, Washington State University Extension Energy Program, 2003.

• The Energy Star publication Improve Energy Efficiency with Desuperheaters describes a heat-reclaim technology often used in warm climates. Desuperheaters are small heat exchangers used with some air conditioners and heat pumps to extract heat as it leaves the compressor. Properly installed, these units can provide most of the hot water for a family at little or no cost during the warm months and, as an extra bonus, the heat pump or air conditioner will run a little more efficiently.

• Heat-pump water heater manufacturers:

• Therma-Stor

• Applied Energy Recovery Systems, Inc.

• Nyle Special Products

• Addison

• Oikos Product Directory, search for heat-pump water heaters.