In another blog I stated that it was better to get a solar hot water heater instead of a add-on heat pump. I have changed my mind. Here is the reasons why.

One, I want to turn off the gas service to my house. Normal solar heat exchanger tanks use electric anyway, but during the winter when the sun does not shine very much I would be using the electric backup a fair amount.

Two, I have limited roof space. Even though solar heating is more efficient then solar electric, electricity is more versatile. With the limit space I would like to devote as much as possible to PV panels.

Three, the add-on heat pumps waste product is cold air. This could help with my AC bill in the summer. Since the water heater is located in an unconditioned space in the basement the waste cooling would have little effect in the winter.

Lastly, if a solar hot water system is designed correctly, in the winter I will need to use the backup heating elements. Then during the summer I will be wasting thermal energy because I simply can not use it. Utilization increased in the summer leads to more backup in the winter. More output in the winter leads to more waste in the summer. With the heat pump feed by future solar electric, there is no waste. What electric I don’t use is given back to utility to use at a later time.

airtapI have purchased a heat pump from Air Generate for $550. I am planning on purchasing an 80 Gallon water heater from Whirlpool. I will not be paying $800 because it is cheaper in my area. I will then mount the heat pump onto the water. Then set it in place. I have the 30amp 240V line already run to the location. I may not even connect the water heater up to 240VAC.  But a nice feature of this water heater is anti-freeze setting. The heat pump runs off 120V. FYI-the reason for the big tank is it has better insulation then a smaller ones and I want to set the temperature at 110 degrees for better heat pump efficiency. Thus the need for more holding capacity. As always I will post the finished product.

Total cost estimates are about $1200. This is about $800 more then if I just replaced my gas unit but I don’t think I will ever run out of hot water. And I get “free” AC in the summer.

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