[Strawbale] More on water heating

[David Neeley]

It seems to me that a continuing discussion of water heating is
beneficial, as too many people make assumptions that can be costly.

There seems no argument that in an appropriate climate with adequate
sunshine, the  most efficient water heaters of all are solar.
Furthermore, there are some that are surprisingly affordable--such as
the Chinese-made evacuated tube collectors that have been as low as
$800 or so for a reasonably-sized unit. It is not difficult to create
a setup that has an incomparable lifecycle cost where there is
sufficient sunlight year-round.

However, if someone is in a Southern location and puts in a heat pump
forced air HVAC system, during the cooling months a desuperheater
added to the heat pump can transfer waste heat into the domestic hot
water, creating the hot water as a "free" byproduct of the cooling
process. This would make even a solar system difficult to
cost-justify.

A freestanding heat pump water heater, too, might be worth
considering. These take heat from the air and put it into the water.
Again, where you are in a cooling climate, this may add a sizable
cooling component to your house while producing the hot water. These
are made both as complete systems and as retrofit add-ons for existing
water tanks.

Regarding tankless heaters--I like them very much where appropriate. I
do not understand their attraction when used with a storage
tank--unless you simply like very high-priced heating elements. I also
do not understand their draw for a radiant heating loop, as their
cost-efficiency suffers in such an application.

In other words, it seems important to look at the entire design and
the site and climate in which it is built to determine what the most
sensible water heating setup might be. It seems by no means a cut and
dried proposition, and no one single type equipment is likely to be
universally the best solution.

David