Domestic Hot Water (DHW) is the water used for hand washing, dish washing, showers and other similar purposes. DHW is separate from the main heating system water (if present) in a building as the water must be potable and once used it leaves the buildings via the drainage systems, typically returning to municipal sewer systems.

DHW is generated by heating cold water from a buildings water supply, sometimes called city water. There are several methods of heating this water that cove.tool supports

  • Electric

    • These are typical in homes and use an electric element to heat incoming water

    • System Efficiency is 0.75

  • VR-Boiler

    • These are standard efficiency fired boilers for DHW. If you have limited information about the projects design VR-Boiler is a conservative assumption.

    • System Efficiency is 0.61

  • Gas Boiler, HR-Boiler

    • These are high efficiency gas boilers which will save energy compared to VR-Boilers.

    • System Efficiency is 0.75

  • Co-Generation

    • This covers DHW generation via a combined heat a power (CHP) system. These are most typically at very large scale and overall not very common.

    • System Efficiency is 0.9

  • District Heating

  • Heat Pump

    • This a newer technology for DHW generation which utilizes an electric heat pump. These provide the highest efficiency for DHW generation.

    • System Efficiency is 1.4

  • Steam

    • This covers DHW generation via steam boilers. Less common in modern buildings.

    • System Efficiency is 0.61

Estimating Costs and Efficiency of Storage, Demand, and Heat Pump Water  Heaters | Department of Energy

 Illustration of a standard domestic VR-Boiler and the smaller electric counterpart.


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