[stevehull]

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You are exactly correct that a heat pump would heat water with 1/4 the energy as compared to a straight resistance type electric heater. The 1/4 number, when expressed as the reciprocal is called the coefficient of performance (COP) and in this case the COP is 4.0

I am designing the plumbing water heating infrastructure for our new house and you can purchase water to water heat pumps with a COP of 5+ with inlet water at 60 F (central Oklahoma) and an output temp 50 F degrees higher (110 F).

This is also about 1/2 the cost of natural gas and 1/4 the cost of propane. A good storage water tank is in the range of $500 and the annual water heating using electricity would be ~ $400. Using the GTHP with a COP of 5 (cost ~ $2) means an annual water heat cost of ~ $80 - or some $320/year in savings or ~ a five year payoff.

And I believe I can make one for a LOT less than $2K!


Steve