"Paul M. Eldridge" wrote:

On Sun, 11 May 2008 09:29:59 -0500, "Pete C."
wrote:


"Paul M. Eldridge" wrote:

On Sat, 10 May 2008 23:11:37 -0500, "Pete C."
wrote:

The other hurdle we need to get past is the all too common idea that if
you can't replace 100% of your energy needs with RE it isn't worth
pursuing at all.

Hi Pete,

This is a critical point and one that causes me endless frustration.
When discussing air source heat pumps, the common objection raised is
that they can't typically satisfy 100 per cent of the home's space
heating demands and for some folks anything less than 100 per cent is
completely unacceptable. What they fail to understand is that you
don't have to satisfy all demand for it to be **cost-effective**; it's
a matter of determining the optimum solution that provides the
greatest **net benefit**. So who cares if you require backup or
auxiliary heat on the three or four coldest days of the year if, at
the end of the day, it has saved you more money than any of the other
alternatives.

We're not all engineers and we don't all hold advanced degrees in
economics, but if more of us understood (and embraced) the concept of
net present value, it would no doubt help us to make better choices.

Cheers,
Paul

Ground source heat pumps take care of that problem for the most part.

Hi Pete,

That may be so, but when you compare the economic performance of a
high-efficiency air source heat pump to that of its geo-based
brethren, the former prevails nine times out of ten and ten times out
of ten if you apply the difference in their respective cost towards
measures that further reduce the home's space conditioning and DHW
requirements.

Admittedly, that's a pretty bold claim but I've run hundreds of
different scenarios using various heat loss factors, weather data,
utility charges, install costs, discount rates, etc. and in my
experience you have to push the assumptions to the far extremes before
you can reverse the results. That said, I'm more than willing to be
proven wrong if someone can provide me with hard data and I certainly
wouldn't object to sharing mine.

Cheers,
Paul

Are you comparing the labor intensive old style deep hole or large
trench array, or the newer much better and much less labor intensive
trenched vertical coil installation?