Varmvattensbehov

Varmvattensbehov is a term used in building and energy engineering to describe the demand for heated water. It encompasses both the volume of hot water consumed by occupants and the energy required to raise the water to the desired supply temperature. In energy calculations, DHW load is typically modeled separately from space heating, ventilation, and cooling, since it affects different parts of the building energy balance.

The demand depends on multiple factors. The number of occupants, daily and hourly usage patterns, the efficiency of domestic fixtures (taps, showers, baths), and the desired hot water temperature all play a role. Climate and seasonal variation can influence hot water consumption, as can routines such as bathing habits and dishwashing. Measurements are commonly expressed as liters per person per day or as annual energy used for hot water (kWh/year). Typical ranges vary by region and housing type, but modern households often aim for lower hot water use through low-flow fittings and shorter shower times.

Estimating varmvattensbehov can be done with simple per-capita methods or more detailed dynamic models that use hourly demand profiles. Accurate estimates require specifying inlet water temperature, target hot water temperature, storage and distribution losses, and the efficiency of the water heating system. The resulting load informs the design and operation of hot water systems, including electric water heaters, gas or district heating, solar thermal, and heat pump configurations.

Strategies to manage varmvattensbehov include using high-efficiency fixtures, short-demand strategies, properly insulated pipes, and coupling hot water production with heat recovery or solar-assisted systems to reduce energy use and peak loads.