Take for example the provision of domestic hot water. In a product approach to energy efficiency regulation, different minimum energy performance standards (MEPS) are set for water heaters, storage tanks, and packages of water heaters and storage tanks. While this approach has its merits, it will take a systems approach to make those components interact in the most efficient way, avoid over-dimensioning, and optimize automation and control. Through a precise estimation of the load pattern of the hot water consumption, the control system can be adjusted so that there is always just enough hot water available when needed while the amount and duration of the hot water storage is minimized. The same system can also be programmed to answer to variable electricity prices, shifting consumption to hours of lower prices. Thanks to the buffer of the storage tank, water heating systems are particularly suitable for Demand Side Management, but it requires an adapted, site-specific design of the storage tank and its control system. If design and installation would only follow a component approach, this opportunity would be neglected.
Looking at the hot water supply as one system also brings new types of energy savings measure in the picture, such as the installation of a waste water heat recovery (WWHR) system. A WWHR system is a simple heat exchanger that uses the hot water drained from a shower to pre-heat the cold water flowing to the water heater. It is mainly used to increase the efficiency of heat pumps, but can also prove worthwhile for other water heating technologies. And since showers are usually taken in the morning or the evening, the efficiency gain does not only reduce primary energy use, but also mitigates the need for expensive peak hour electricity.