I’ve been looking into hot water recirc options for a distant kitchen sink for a whole-house remodel. Of the various options for a recirc loop (gravity, continuous pump, timed pump, and demand pump), the demand pump appears to be the most energy efficient. However, you still need to hit a switch and wait for the hot water to get to the location of use. You save the water that would have gone down the drain, but you’re still waiting.

Would it be possible, instead, to install a small electric tankless point-of-use heater below the sink with the hot water line hooked up to the cold inlet on the heater and the hot outlet on the heater going to the faucet? You’d then have instant hot water and if the small heater’s set point is lower (10-15 degrees) than the temp of the water coming from the main water heater, the unit would stop running once the house hot water got to the small tankless heater/sink. No extra water down the drain, no waiting, and minimal additional energy use. And no warm water in the cold line (if I use that for the return to the main water heater).

The small electric point-of-use heaters are relatively inexpensive and would be less expensive than a recirc pump, check valve, and the demand switch. Or at least comparable.

Just wondering if I’m missing anything here. Thoughts? Is this an improper use of a mini tankless?

Cheers,
Jason