[irjustin]

Water heating, like cooking should not be a significant part of the home power equation when done right.

Large boilers need to die. Small "instant heaters" at or very close to each faucet is the correct way. Way way way less energy usage.

Sadly the electrical water heater units usually don't have access to the 240v line and are limited to 120v, 10A or something measly. People then complain their water doesn't heat fast enough or get hot enough for a given flow and then complain/swear off small instant heaters =/

[sagarm]

Just did the math and supporting a ~70F (50F-> 120F) rise at 1GPM (faucets are limited to about this) requires 9kW, or about 40A at 240W. Supporting a bunch of 40A circuits in a typical home would require a massively upgraded circuit panel for most homes -- 200A or even 100A service is common.

A centralized system avoids having multiple circuits with potentially high loads like this. Not to mention the likely gigantic heat exchangers required to transfer 9kW!