Conversation

Been asked a question about small under sink water heaters. These I have never dealt with. Issue is bathroom far from water heater, where it can take minutes of wasted water to get any hot water at the sink. Researching this some, I see that there are tank type (which I assume will be less energy efficient since they'll be using power to keep the water hot, even if the tank is only a couple of gallons), and tankless, which appear to be out of scope due to power requirements. Tank type apparently can plug easily into an existing 20 amp circuit with watts to spare, tankless far more likely to pull too much power on existing circuits. I've also seen systems that run water as its heating back through the cold water line, but I've also seen discussion of this wearing out pipes. Ugh. So tankless units (presumably rated so that they can tolerate hot water from the main tank on their input?) seem more sensible as a suggestion, but any thoughts would be appreciated. Thanks!