Heat Pump vs Standard
July 26, 2005 8:59 PM   Subscribe

Our air conditioner is going out and has to be replaced. We are likely going to replace it with two standard units as the single unit has never heated or cooled the entire house evenly. The heating/air guy said that would be ideal but would cost 8-10 thousand vs 4 thousand or less if we just bought a new 5 ton unit. However the electric company is offering to loan people the money if they want to buy heat pumps. Not having a lot of extra money right now, that is tempting IF heat pumps are likely to do the job, which I am not sure about.

I live in northwest Arkansas and while the average daytime temps in winter are in the upper thirties or lower forties, we frequently have nights that reach the teens or below and in the past have had subzero temperatures, although the last few winters have been mild. I have read that heat pumps are not ideal when the winter temps are cold but I have also read that newer heat pumps are much better at handling cold weather than older models. Any advice, especially from those who own heat pumps would be appreciated.
posted by weretable and the undead chairs to Home & Garden (10 answers total) 1 user marked this as a favorite
Heat pumps are ungodly expensive to run. And this is coming from someone living in Ontario, Canada, about the cheapest place to buy electricity in North America. IMHO, avoid at all costs.

[I'm not surprised the electric company would do this much to get you into a heat pump, hell, if I were them I'd give the damn things away at the price of electricity!]

As far as being able to cool well, I can assure you they work just fine (apart from the expense) Ours worked fine the very few times we used it about a decade ago, and where I live temperatures could reach -20 C (-4 F, apparently).
posted by shepd at 9:14 PM on July 26, 2005

Heat pumps are just air conditioners that can be used to move heat in either direction. They are awful as heaters, because there's so little heat outside in the winter (the coils freeze up and the heat pump actually has to run in air conditioning mode for a while to melt it). But compared to an air conditioner, well, a heat pump IS an air conditioner, it shouldn't be any less expensive or any worse at cooling the house than a normal air conditioner.
posted by kindall at 10:00 PM on July 26, 2005

Any chance you have a well on your property? My dad has an old house with a well on it and fifteen years ago or so the local utility company came out and hooked up some sort of air pump to pump air down into the well to cool it. The heater/AC then pumps the air back up to the house and heats/cools the house from that below-ground standard temperature. I don't remember it being cheap, but it is damn cool.

The air in the well is like 60 degrees or something so the heater actually has to run year round. In the summer, you have to heat the house up from 60 to 68 or 70 or something like that, however heating it up 10 degrees is a hell of a lot cheaper than using AC on a huge old house to drop the temperature 30 degrees. Likewise in the winter, the heat is on to bring it up to 70 - 75 degrees, but again that's cheaper than bringing it up from the outside temperature of 30 - 50 degrees.

Good luck.
posted by pwb503 at 10:21 PM on July 26, 2005

I don't remember it being cheap, but it is damn cool.

When I was there, Cornell University was doing this on a massive scale. Take that, your dad's well!

Since we've established that heat pumps are basically reversible air conditioners, could you just take the electric company's loan, install a heat pump, and then just not use it during the winter? Or have they thought of and ruled out that possibility?
posted by trevyn at 10:48 PM on July 26, 2005

I have a system with two heat pumps similar to what you are thinking about and I reccommend it. I have had to replace both heat pumps over the last few years (the originals were 15 years old and wearing out) and so have already done some research on the subject. I live in GA, so my climate is probably pretty similar to yours. Heat pumps are good for heating until the outside temp gets to 35 deg. F or so, then the auxillary heat kicks in and really eats up power. That is why heat pumps are not so hot for northern climates. Other factors to consider: With two systems and programmable thermostats, you only heat/cool the areas where people are at any given time with potential energy savings. Look at the SEER ratings, get the highest you can afford as they will really pay for themselves in energy savings over the life of the unit. Ask about which refrigerants are available; you have a choice between freon and the newer ozone-friendly versions that can make a difference in both initial cost and maintainence cost. Finally, if you are interested in the cold air from the ground method, those are geothermal heat pumps and are becoming more common.
posted by TedW at 5:37 AM on July 27, 2005

One other thing, this is also an ideal time to look a the overall quality of your insulation, door and window seals, and so on. If you have a well insulated house, it will retain heat through the cold nights during winter, making you less reliant on the heat pump for heating.
posted by TedW at 5:41 AM on July 27, 2005

The people telling you heat pumps don't work worth a damn are probably in cold climates. It's not really your best choice if you have long, cold winters. But if you live somewhere fairly temperate, they're probably your best bet. As someone stated above, the geothermal or ground-loop heat pumps pretty effectively solve the cold weather heat problem, since the ground below the frost line stays at a pretty constant temperature.

A side benefit of the geothermal heat pump is that you can route the coolant coils through your hot water heater, which results in free hot water during the summer.
posted by electroboy at 7:03 AM on July 27, 2005

My father took advantage of a Florida Power & Light rebate back in the late 80s/early 90s for an air conditioner unit that used the pool water to assist in heat exchange. Being an endless tinkerer he constructed the pipes in such a way that he could turn a few valves (in a sequence that nobody but him can follow to this day) to switch it from recirculating pool water to instead running the well pump and 'venting' through the sprinkler system.

This turned out to be a brilliant move since the pool will only contain so much heat, particularly in a Florida summer. The water would eventually be heated to the point where it would accomplish nothing with regards to siphoning the heat from the AC compressor side of the system. The AC would still work okay in that situation but it wouldn't gain any of the efficiency that was the whole point of this boondoggle.
posted by phearlez at 8:02 AM on July 27, 2005

I live in Kentucky, where the climate is similar to yours (although the summer is not so long), in an 1890s 2-story house. The house was built as a 1-story with an attic, but sometime in the 1930s the attic was finished. When I bought it there was one gas furnace and central air conditioner. This was fine on the ground floor but totally ineffective upstairs (as in, hotter than outside in the summer and almost as cold as outside in the winter).

Two years ago I had to replace the furnace, and the HVAC guys assured me that a bigger, better, state of the art unit would solve the problem. It didn't. Last year I had a heat pump installed for the 2nd floor. It works only to supplement the main central unit, and it does very well. It's hard to calculate how much more I am paying in utility bills since I also replaced the windows, put insulation everywhere, and no longer have to use window ACs or space heaters. On the other hand, I had to have most of the house rewired and the service doubled from 100 to 200 amps in order to handle the extra load. Since it doubles the usable space of the house, I think it's worth it.
posted by Alylex at 11:23 AM on July 27, 2005

Here in British Columbia there are incentives from various places to buy heat pumps as well, so we have been considering one as well.

A lot of these comments though complain about using the heat pump to heat the house during the winter. What if you intend to use your gas furnace for heating during the winter and just want to use the heat pump for cooling during the summer? In other words, is a heat pump likely to be more efficient/cost effective at cooling that an AC unit.
posted by GeneticFreek at 2:36 PM on July 27, 2005

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