I was under the impression that ground source heat pumps was the way to go for heating and cooling one’s home in terms of carbon foot print and economics of annual energy costs. However, I ran across a study completed by MichealsEnegy for the Minnesota Department of commerce that shows the contrary. Here is the link to the study: http://www.michaelsenergy.com/2010/06/minnesota-geothermal-heat-pumps/ Unless I’m reading it wrong, GSHP technology is not very advantageous. I’m interested in how others interpret the data.

Not sure if their model of 14.1 EER and 3.3 COP are a great model to use or not for GHP performance numbers. Seems most on the market now do better than that.
I did not see an indication whether they accounted for the 30% federal tax credit, but I admit I only skimmed the article.
I did see their numbers make sense for a small house (in terms of cost), maybe not for carbon footprint. Carbon footprint is highly dependent on electric utilities generation sources though.
Also, this study applies to natural gas availability. May be commonplace in Minnesota, but non-existent in my neck of the woods.
Run it with propane or oil and it will change.
That is why each install needs a good load calculation, good comparison of available options for the area, computation of utility costs based on where you are, reasonable numbers for the equipment specificed.

Didn't read all 113 pgs, but under small resident new construction, they state 25,000 KWHs used in a year. My small residence(1920 sq ft 1st floor) used 14,500 KWHs and thats total for the house not just the HVAC. HVAC about half 7,600 KWHs.

Study is from 2008, I think 30% fed tax credit came after.

I don't buy the carbon foot print increase,

"The installation of GHP systems in all building types and sizes increases other pollution, including sulfur dioxide,
particulate matter, and mercury, when compared with conventional HVAC systems."

"Because the study did not evaluate performance of individual
systems, further study of actual system performance in Minnesota would provide a better basis
to further evaluate the potential benefits of GHP systems within Minnesota."

ChrisJ

The local grid sources make a huge difference, and MN has traditionally been heavy on the coal end, in which case even at an average COP of 4 (good luck with that!) you'd have a higher carbon footprint than condensing gas at equivalent delivered-BTU to the house, with all of the other coal emissions on top.

http://www.eia.gov/electricity/state/minnesota/

As of 2010 data coal was behind just over half of all kwh delivered to the MN grid:

http://www.eia.gov/electricity/state/minnesota/xls/sept05mn.xls

Mind you, combined cycle gas and wind power is rapidly displacing other power generation in MN (with a much smaller but still measurable kicker from solar. As the grid greens-up, so does the GSHP. But I doubt at typical GSHP efficiencies in that colder-dirt region the carbon footprint has yet to drop below that of condensing gas. But at the rate of wind power development in the state that may very well change before 2020, especially if carbon gets taxed, rendering some of the crummier/older coal plants uneconomic.

If you had told me 7 years ago that a quarter of all power sold in Iowa in 2012 would come from wind I would have invited you to stop smokin' that stuff (and please, step away from me! :-) ) but over the past 25 years all IEA and EIA projections have undershot the deployment rate of renewables- the transition to renewables worldwide is happening even faster than the analysts are prone to believing:

http://www.greentechmedia.com/articles/read/conventional-wisdom-about-clean-energy-is-way-out-of-date

MN is stepping up, rather than slowing down the implementation of PV & wind:

http://www.greentechmedia.com/articles/read/minnesota-is-a-governors-signature-away-from-450mw-of-solar

So, will GSHP in MN be carbon net-negative relative to condensing gas over a 20-25 year lifecycle? Don't bet on it, even if it might be for the first 5 years. When that report was published in 2008 it sure looked net-negative, but that was before natural gas prices bottomed out and the lifecycle $/Twh of wind power dropped to that of 30% efficiency thermal-coal generation. The grid in the upper midwest has changed in the past 5 years, and it's just getting started. Every year wind turbine technology is getting incrementally more efficient, and incrementally cheaper- cheaper than 35% efficiency gas fired power at contracted-for long term gas pricing, and right in there with 50%+ combined cycle gas power for lifecycle costs. Doesn't take much of a carbon emissions tariff to turn this steady stream of development into a torrent, since natural gas contract pricing is already driving the wind market for wind in some places. Coal? What was that? The 19th & 20th century driver of the industrial revolution is just to dirty to drive 21st century expansion, especially when what had been externalities begin to be paid for directly by the industry.

Kind of a BS study. They modeled and calculated everything, and with an average COP of 2.6 - 2.7, and with an average EER of 12.4-12.7 for a small new constructed house with geo. That way I can make every study fail.

ground source heat pumps was the way to go for heating and cooling one’s home in terms of carbon foot print and economics of annual energy costs

They are, except for the effects of coal plants and upfront costs.