Control of DHW storage charging (with solar collector and supplementary heat generation)

What does DHW-1d measure?

DHW-1d is a smart-ready service within the Hot water domain of the Smart Readiness Indicator (SRI). The service examines how a building controls the charging of domestic hot water storage when both a solar collector and supplementary heat generation are present.

The principle is that solar energy takes priority over other heat sources. The question is how automatically and precisely a building management system (BMS) manages that priority, and whether the system considers actual demand and multiple readings in the storage tank.

What functionality levels are available?

The service has four levels, numbered 0 to 3. At level 0, a user manually selects whether solar energy or supplementary heat generation is used. There is no automatic control.

At level 1, the system controls charging automatically: solar energy receives priority, and the supplementary heat source supplements as needed. Level 2 adds demand-driven supply, or storage management based on multiple sensors.

Level 3 is the highest level within this service. Here the system not only controls charging automatically, but also regulates supply and return temperature based on demand, combined with multi-sensor storage management.

How does this count toward the SRI score?

Each smart-ready service is assessed against seven impact criteria, such as energy efficiency and comfort. This assessment takes place through three key functionalities that carry equal weight in the final score.

The score of all services combined determines the building class, ranging from below 20 percent to 90 to 100 percent. This service is not part of the simplified method A, only of the full method B with 54 services.