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DHW Generation

Engineering Inputs: Domestic Hot Water Generation

Patrick Chopson avatar
Written by Patrick Chopson
Updated over 4 months ago

Domestic Hot Water (DHW) is the water used for handwashing, dishwashing, 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 analysis.tool supports

  • Electric

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

    • System Efficiency is 0.92

  • 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 0.78

  • 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 and power (CHP) system. These are most typically at a very large scale and overall not very common.

    • System Efficiency is 0.83

  • District Heating

  • Electric Heat Pump (Low-efficiency)

    • This is a relatively newer technology for domestic hot water (DHW) generation representing an advanced approach, utilizing an electric heat pump. It offers three tiers of efficiency: low, mid, and high.

    • Electric Heat Pump, low efficiency: 1.4

  • Electric Heat Pump (Mid-efficiency)

    • This is a relatively newer technology for domestic hot water (DHW) generation representing an advanced approach, utilizing an electric heat pump. It offers three tiers of efficiency: low, mid, and high.

    • Electric Heat Pump, mid-efficiency: 3.0

  • Electric Heat Pump (High-efficiency)

    • This is a relatively newer technology for domestic hot water (DHW) generation representing an advanced approach, utilizing an electric heat pump. It offers three tiers of efficiency: low, mid, and high.

    • Electric Heat Pump, high-efficiency: 4.0

  • 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 instantaneous counterpart.

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