Some of the most promising technologies in the thrust towards more efficient heating and cooling are advances in heat pumps. A great example of this is Hallowell's Acadia heat pump, designed to extract heat from the air of even a northern winter. Historically, "air-to-air" heat pumps don't offer quite the heating "efficiency" of ground-sourced, geothermal heat pumps because they have to extract heat from air that is far colder than the earth temperature. That said, they are easier and cheaper to install, requiring about the same installation as central air conditioning. Plus, in a July 2009 article by Lauren Hunter at Remodeling magazine, Hallowell claims their air-to-air system can be even more energy efficient than geothermal in cold weather performance. That seems to me to violate laws of thermodynamics, but the universe may have written escape clauses in these laws since I went to school.

The trouble is, Hallowell is not competing with geothermal systems on a level playing field at the moment -- simply due to oversight.

In the necessary haste to keep a teetering world economy from imploding, it appears that the drafters of the energy portion of the US economic stimulus legislation relied on existing industry standards for high-efficiency heat pumps. That's not unreasonable, but unfortunately these standards covered only high-efficiency two-stage heat pumps, leaving out the possibility of more stages. The Acadia is a three-stage heat pump, and works even better than two-stage pumps -- but the tests required to qualify for the unlimited 30% tax credit have to treat it as a two-stage machine! Not surprisingly, it didn't qualify, as it was never designed to run that way. (It does qualify for an EPA Energy Star rating.)

It's as if gas-mileage standards had been written for four-speed transmissions. Fifth gear (or "overdrive" as it used to be known) makes many of today's small-engine cars efficient. If they had to be tested using only the first four gears, they wouldn't measure up.

This omission is, apparently, in the course of being rectified by waivers, but in the meantime Hallowell is losing sales it should have won. It is a very attractive system according to an owner whose home I visited. So don't write it off -- check it out, check out the latest in the tax credit / waiver situation with Hallowell, and see if it might be the system you need.