As I have stated in my first two posts I am new to geothermal so please go easy.

How is payback calculated?  I have visited several web sites that seem to be stating unrealistic payback times.  I do not see how a system that costs 30K to install and saves 2k a year has a payback of 6 years.  By my calculations the pay back is 15 years...2k a year for 15 years = 30k, correct?

Thanks

One big factor that gets overlooked on a new project is the cost of the conventional system that you don't have to buy when you do geothermal.  There is no doubt that on a retrofit payback will be longer.  You also have to factor in increases in energy costs to get a better idea. Tax credits and incentives also have to be factored in.

There should be no doubt that a geo system will save you money.  They operate at 300% efficiency.  This is fact and well proven and documented.  Whatever you have now can't be more than 80% efficient.  If you know what your energy costs are now,  multiply them by .40.  This will give you a pretty good idea of what it will cost you to run the heat pump.  Or multiply by .60 and this will be close to your savings.



But think of it this way.  If you have a vehicle that gets 10 mpg  and you can buy a newer vehicle  that gets 40 mpg it shoudn't be too hard to figure out if it makes sense to upgrade.

I just bought a vehicle that runs on natural gas.  I can buy natural gas for $.68 a gallon.  I drive 500 - 800 miles a week.   I can now fill up my tank for $20 instead of $140. It didn't take me long at all to know that it made sense to buy the natural gas vehicle.

I have attached a payback analysis that we did for a customer.  His projected payback is 6.5 years.  I have done other payback analysis where the breakeven point is 14 years.  There are a lot variables that go into the final payback.

I am afraid you will not find the kind of info you are looking for.   Any info you do find will not apply in your case since your building is not the same  as the case study you look at.

Given the right data for your building,  a designer  could calculate a payback.  Without the data it would only be a guess.

Hope this helps. 

I could do a sort of guesstimated payback if we had the following info (hopefully I don't miss something):
-accurate heating and cooling loads;
-occupancy type of building;
-electricity costs;
-gas/fuel oil/propane costs;
-efficiency of existing systems;
-type of existing systems
-total price of the geothermal system install
-type and efficiency of the geothermal systems (I could generalize this)
-type of funding for the geothermal system
-location of the building (city...)

There's a wonderful program that does the calculations with this info. It's Elite's Energy Audit program.

The tough part on a large building is the accurate load calculations. One way to get around that using the Audit program is to use the existing system's heating and cooling bills. However, it's not that easy to discern how much of a heating bill or cooling bill there is when it's lumped in with the rest of the building's electrical use.

slfriedm,

I think this might give you an idea of cost savings.

Btu's at 100% Efficiency Typical Efficiency

Fuel Oil = 140,000 / Gal. 80%
Natural Gas = 1,000,000 / 1000 Cubic FT. 80% to 90%
Propane = 91,600 / Gal. 80%
Electric = 3,413 / KWH 100% (Resistance Heat)

Do the following calculations with the type of fuel you are using. Getting the anual usage off your past bills. This way you compare savings on actual usage, providing you can separate how much of your bill is heating. This doesn't mean you can't make other improvements to the building, such as insulation, better windows, etc..

Working Example:

I used 700 gal. fuel oil from 3/30/07 to 3/30/08

700 gals. x $3.80/gal. = $2660.00

140,000 btu's x 80%Efficiency = 112,000 btu's

700 gals. x 112,000 btu's = 78,400,000 btu's
................................................................
Geothermal

At a minimum I believe you should get 300% efficiency, DX could get 500% to 600%. Heat Pumps use electricity.
Which translates to 300% x 1kwh 3,412 btu's = 10,236 btu's per KWH.

Total Oil 78,400,000 btu's / 10,236 Geo. btu's per kwh = 7,660 KWH

7,660 KWH x $.08 per KWH(Put your electric rate here) = $612.80 Total Geothermal Price

$2660.00 Oil - $612.80 Geo = $2047.20 Savings per year.

This is just direct fuel cost savings, and doesn't include burner cleaning or service.

If geodean or tuffluck don't agree please let me know.

Paul Campbell

Thanks.  That does clear things up for me.  I guess my problem is that there are no standard numbers and there are a lot of unknowns.  There is no way I will be able to convince anyone to look further at geothermal because they are very traditional and do no like unknowns. 

Thanks again.