Alternative Energy Blog reader Bruce Stenswick from Minnesota emailed me about his experience of installing a ground source heat pump. Here's what he says to say:
For the winter of 2003-2004, from early October to early May I used 7620 kwh of electricity. That is equivalent to 26MBtu of natural gas. My heat pump has a coefficient of performance of 3.3, which means I needed 26 x 3.3 = 85 MBtu of heat for the winter. In order to obtain that amount of heat from a 95% efficient natural gas furnace, I would have to purchase 85/.95 = 90 Mbtu of natural gas. 95% efficient is close to the tops in efficiency. Natural gas this last winter varied from $8.60 to $9.90 /MBtu. At $9.50, 90 MBtu is $850. The 7620 kwh of electricity at Xcel Energy's electric space heating rate of $0.054...../kwh would be $413. So I cut my heating bill in half.
From an energy perspective, I assume a 35% efficient power plant and 7% line losses. Doing the calculations on this I come up with 80 MBtu of natural gas needed to produce the 7620 kwh of electricity delivered to my house.
From a CO2 perspective, I calculate I cut my CO2 output about 30%. 11% because of the efficiency gain, and another 20% due the fact that Minnesota gets 20% of it electricity from sources that do not produce CO2, mostly nuclear.
Other pollutants, I have no idea how to calculate.
In reality, I like to claim I put nothing into the air when I heat my house. I buy all of my electricity from Xcel Energy's WindSource program, which means I pay $0.02/kwh extra. Xcel then goes out and buys or builds that much extra wind energy above and beyond what has been mandated by the legislature. Even doing that, I still cut my heating bill 33%.
These numbers might not hold for everyone. Heat pumps do not work well in cold temperatures with setback thermostats. That does not affect me since someone is always home and the thermostat is never below 68 in the winter. People with setback thermostats often have the house at 60 when no one is home.
This is an overlooked area. At the gas rates we had this winter, I cut my heating bill in half because of the low electric rates that utilities give for heating with electricity. My house was a retrofit. Geothermal heat pumps beat the pants off of natural gas if you are building from scratch and can put in radiant floor heat.
(please note I haven't verified his figures)
Grants for Geothermal Ground Source Heat Pumps
Author of The Tipping Point & Blink on Geothermal Energy
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