Posted by (PeteCresswell) on June 24, 2009, 5:51 pm
From the outside it looks like one hopes to recoup the additional
up front cost via savings on whatever fuel/means are currently
used to heat/cool the house.
In our case that would be natural gas for winter heating and
electricity for summer cooling.
Seems like there are three cost factors over and above the diff
between cost of electricity to drive the heat pump and cost of
currently-used heating/cooling energy sources:
1) 30% no-limit tax deduction for the up front cost.
2) Relative increases in the cost of electricity and
3) Whatever inflation comes out of the current fiscal
For #2, it seems like one is betting that the cost increases of
natural gas and electric power will move upwards more-or-less in
sync - as opposed to electric power going through the roof and
natural gas staying about the same.
Has anybody looked into the underlying economic assumptions?
Posted by vaughn on June 24, 2009, 6:45 pm
I can quickly think of more factors that you left out. A few are:
4) Cost of capital. (An expensive item too often left out of alternative
energy sales pitches)
5) Relative costs of maintenance between the two systems.
6) RISK! Design and installation of geothermal systems is not an exact
science. A) Problems with underground systems can be very expensive fix.
Expense and downtime could be much greater than for a conventional system.
B) If the system is not sized properly, backup heating can be an unexpected
None of the above should be taken as "killer" arguments against these
systems, just as factors to be soberly considered.
Posted by Ecnerwal on June 25, 2009, 2:00 am
Actually a credit, I believe. That's a good thing - credits are much
better than deductions. Money off your taxes, rather than money off your
taxable income. But it still doesn't make spending way too much make
sense...probably 30% or more got tacked onto most units as soon as the
tax credits went through.
Not likely to be a lot of variation - if NG is cheap, electricity will
be made with NG...
The one I looked into was rather gagging on this aspect - $0K, plus
installation (I was looking at a use pattern which fit my needs of being
able to either pump from or recirculate in my well - if adding a well or
two or a ground loop to the costs, quite a few more kilobucks are
involved). What's irritating is that the guts are very similar to
split-system heat pump/ac units, which (when air cooled/coupled, rather
than water cooled/coupled) can be had for $-2000 in the size I need
(not very large, due to vast insulation).
When I had an NG furnace, it was one of the most trouble-free items I've
ever had. No NG where I'm at now. Propane, perhaps, but the price seems
high relative to other fuels these days. AC/Heat pumps seem to need
regular servicing to stay running, and certainly have more complex parts.
What you might want to look at as a much less money in, potential
savings out (as you have AC now, and presumably use it) is a
desuperheater, which I gather (from another group - I don't have central
air) can be added to your central air system and basically makes you
free hot water when you use the AC, and presumably also makes the AC run
a bit more efficiently, at least when it's heating water.
Cats, coffee, chocolate...vices to live by
Posted by harry on June 24, 2009, 7:51 pm
Tsk tsk! They are becoming increasingly common in the UK. The big
expense is digging the hole to bury the outside heat exchanger. (Or
drilling the deep holes) & of course putting the lawn back as it
They can often be reversed to give cooling in Summer and pre-heat the
ground outside ready for Winter heating. They require no maintentance
By only having one fuel (ie no gas) you avoid paying the premium rate
on two fuels. (That is the first part of any fuel you use is charged
more for. Or they charge "meter rental".)
The coeficient of performance is in the order of 5 or 6 these days.
(ie for very Kwh of electricity you put in you get five or six of heat
Ther is an alternative cheaper system has air heat exchangers outside
instead of in the ground. But they only work down to about 20degF
Minus 5degC outside air temp.
I looked into all this myself but decided to go down the road of
massive insulation. Which can never go wrong.
As to the cost of fuel, it can only go up.
A disadvantage with electricity is that if it goes off you are
stuffed. I have a small wood stove. I can store as much fuel as I
like, I can cook & heat water on the stove too. I only use free
wood :-) I just have this theory that in the near future power
cuts will be more common than they are now. So you need a heat source
that doesn't depend on it.
Posted by News on June 25, 2009, 8:11 am
Very wise. Ground heat pumps can be very expensive to install and only cost
the same as natural gas on average to run. The money can go to heavy
insulation, insulated sealed doors/windows etc. Air sourced are a waste of
money, unless the unit is in a warm air stream, like heat recovery extract.
A small backup genny can do to give essential services in the house. A
superinsulated house needs little heat. A superinsulated house can have a
small electric heater. OK electricity is the UK is approx 3 to 4 times the
cost of gas per kW. Installation cost is so low and used so rarely running
costs as still low.