I bought this system, but it's been sitting in a box for about a year. Basically mounting issues and I want it under the rafters rather than under the sink. Ports are in place. Did that when I replaced some valves even before I got the system.
Advanced Conservation Technologies: D'MAND Hot Water Systems
Ballengerb1 of AMHD likes it too.
Rather unique.
My plans initially are wireless control (Black & Decker) using a system I already have for a kitchen and bath location.
Later, I plan to integrate a motion sensor to an 8-channel alarm receiver. One channel will be a wireless doorbell. Yep, using security, supervised transmitters, for a doorbell.
That's in progress too. Got the 8 channel alarm module and started modifying an existing doorbell button to hold a different transmitter.
Anyway, the idea with this gizmo is that they sell a motion activated one, so for a bathroom it's perfect. Walk in. Motion det turns on pump. Pump turns off based on sensing the hot water at the cold water line. Use the facilities when that's going on and warm water should be available to wash the hands. Should also help in the shower. There is an temperature compensated auto-mixing valve there which already saves water.
Kitchen would be on demand. A wireless module that already controls an exterior light will have a channel dedicated to start the circulator pump.
There is a 1/2 bath that I don't care about. The washer and laundry sink are within 10' of the water heater.
Good news: I started selecting the mounting parts. They definitely don't make it easy.
Generally the system is installed at the LAST fixture in the house and pumps the water in the hot water line back into the tank through the cold water line until it's above a certain temperature on demand, thus there is little wasted energy.
You can easily "anticipate" water usage in a bathroom and push a button a few minutes before the intended use. Just how long it takes depends on pipe length and diameter, but shouldn't take over a few minutes.