The hot water challenge

Gary and site supervisor Jesse Heilig
walking through Casa Aguila

Have you ever looked forward to a relaxing warm shower, only to find you need to run cold water for minutes before hot water finally arrives? Not only is it an inconvenience, but it is a significant waste of a precious resource. We were lucky enough to have Gary Klein, the nation’s leading hot water distribution expert, out at our Casa Aguila site to discuss energy and water conservation strategies. Our goal with Gary was to develop a hot water system for the project that wastes less than one cup of water while waiting for hot water to arrive at the faucet.

Gary Klein,  Former California Energy Commission

Domestic hot water accounts for about 30% of household energy consumption, so there is substantial opportunity to conserve energy and resources by increasing the efficiency of the hot water distribution system. An ideal system would 1) have hot water almost instantaneously, 2) have safe water (not too hot, no harmful bacteria), and 3) never run out. In larger homes such as Casa Aguila, supplying immediate hot water is a challenge because fixtures are often located far from the water heater.

We discussed installing a hot water recirculation pump throughout the house so when the fixture is turned on it has a hot water supply adjacent to it. However, then we needed to address how much water and energy would be spent recirculating and heating the water during long periods of time when no one is using the facilities, such as when the homeowners are normally sleeping. For this concern we explored the ideas of time and motion sensors, or a manual switch, so that ideally the pump would only run right before someone would need it. We look forward to testing the system!