" wrote:
On Sep 26, 6:03 pm, "Pete C." wrote:
dpb wrote:

On 9/26/2012 3:39 PM, wrote:
...

I generally agree that a geothermal system is probably an
advantage to a house. But it also would depend on where
the house is located climate wise and the cost of electricity
there versus alternate fuels. Here in NJ with electric at 18c
it may not look as good compared to nat gas as someplace
where it's 10c.

Well, of course, but the choice here isn't against competing systems for
a new install; it's already in. Unless it was a case of a demo house or
the like one would presume at least some of those considerations went
into the choice.

And the age of the system and the replacement cost. I know
a lot of the big cost is the outside part, but I wonder how much
replacement of just the inside heat pump part costs as compared
to replacing a gas furnace/AC unit?

Well, that's true for any system, whatever the type. Have you priced a
hi-eff gas system recently? You also get "free" A/C w/ the heat
pump--don't forget to add in the cost there in the replacement as well.
And, if the A/C is used, many have the option of using the waste heat
there for water heating that is another input energy cost reducer. In
TN for the entire summer months and much of spring and well into fall
the water heating was essentially free. Obviously that's not as big a
deal as one gets more and more into more temperate climates so I'd not
expect a unit in PA to have it.

I'm not saying it's always going to be the best possible choice or that
even in this case it's a real plus but I'd surely think odds are it's a
positive as opposed to run-of-the-mill furnace you'd find in the average
house on the block for sale.

All in all, though, after my experience, I'm sold on the concept...

--

A few things to keep in mind:

- Heat pumps in general are pretty efficient these days, and of course
provide both heating and cooling.

- In heating mode, an air source heat pump becomes inefficient as the
air temperature nears the freezing point.

That depends on your definition of inefficient. In a thermodynamic
sense today's heat pumps deliver more heat output even in the
single digits than an equivalent electric resistance heater, which is
100% efficient. At 32F they are probably delivering at least 2.5 X
the heat
of a resistance heater. The total output decreases as well, which
is a potentially bigger problem.






Ground source heat pumps don't
have this limitation since soil temperatures at the loop depth don't get
that cold.

- In cooling mode, an air source heat pump becomes inefficient when the
air temperature gets above a certain point and the heat pump has
difficulty dumping the heat it's moving into the air.

Whatever temp that occurs at, it's apparenty not a problem in a
practical sense because AC works OK at 110F in Arizona.




It's been over 30 years, but I remember people talking how it cost them per
month for refrigerated air. Hundreds of dollars. What does it cost now in
the desert ?
It costs me roughly $25 a month in Pittsburgh. I know the units are a lot
more efficient.

Greg