Domestic hot water

What does the domestic hot water domain cover?

The domestic hot water domain concerns the boiler or storage tank in a building. This component of the Smart Readiness Indicator (SRI) assesses how intelligently the system heats and manages water.

The methodology distinguishes five smart-ready services within this domain. Each service receives a functionality level from 0 to 4, where a higher level indicates greater automation and control.

Which services are assessed?

DHW-1a examines load control of domestic hot water storage for direct electric heating or an integrated heat pump. The lowest level is simple on/off switching; the highest combines time-based load release with demand-driven temperature control.

DHW-1b assesses whether storage charging accounts for locally generated renewable energy or electricity grid signals, such as demand response. DHW-1d does this specifically for systems with a solar collector and backup heat generation, rewarding automatic control that prioritises solar energy first.

DHW-2b concerns priority setting when a building has multiple domestic hot water generators, for example solar energy alongside a fossil fuel boiler. The highest level controls based on current and predicted load, efficiency, CO2 emissions, and external grid signals. DHW-3 assesses performance reporting, from simple display of current values to performance evaluation with forecasting and fault detection.

Why does this domain count toward the score?

Each smart-ready service is linked to seven impact criteria and three key functionalities with equal weighting. This means domestic hot water contributes to the building's overall SRI score, along with eight other domains.

The final score falls into one of seven classes, from below 20 percent to 90 to 100 percent. A building that loads this domain intelligently based on solar energy or grid signals typically scores higher than one with only simple on/off control.