Wash my hands, turn on the hot water, cold water ok. I'll wait...waiting...waiting...waiting...still cold water...1 minute later I just gave up. So I wash my hands with cold water.
Taking a shower is even more of an excruciating experience. First, waiting for the hot water, then getting a blast of cold water during the middle of a hot shower...then back to hot. Turning off the water during the middle of a shower is a bad idea....wait for the hot water again, oh another blast of cold water.
Not impressed with this technology at the moment. Perhaps you have to get into the high-end-very expensive units...I dunno. What you save in energy, you burn a lot in water consumption. I probably used double the amount of water to shower and triple the amount for washing my hands.