buffalobill wrote:
in general: for family with kids, electric tanks are slow recovery so
you get the biggest one you can afford that fits into the space and the
electrical service available.
"On demand hot water system? from Noah Lamy The relative energy
efficiency of these systems depends a lot on other factors such as the
amount of heat loss from a more traditional storage tank system or the
length of time hot water is stored before it is used. In practice they
require a good deal more energy per volume of heated water than
conventional systems


Anybody figure out how an on demand unit could require a good deal more
energy per volume of heated water? I could see how that might be
possible if one were comparing only gas units. It's possible the gas
tank type heater would be more efficient, recovering more of the
combustion heat. But I tend to doubt it could be a good deal more. As
for electric units, they are going to use exactly the same amount of
energy to raise water termp.




and they cannot usually provide enough hot water
for more than one fixture at a time. The traditional storage tank type
of water heater can be quite efficient if the tank and the hot water
pipes are properly insulated.
The on-demand type heaters have their uses in the appropriate
situation. I have found them practical and efficient in situations
where hot water is used only occasionally such as in some shop
situations or where a fixture is at a considerable distance from a
traditional storage tank water heater, such as in a guest house or pool
house. They can also be handy if you are adding hot water to a
structure that has been cold-water-only and the cost or inconvenience
of adding a complete hot water piping system will be prohibitive." it
says at: