When my wife and I first moved into this house, we wanted to add an air conditioner. Seattle is full of people who tell you that “you don’t need an air conditioner”. They’re in deep denial. The beauty of air conditioning in Seattle is that the cost of running an air conditioner is proportional to how hard it has to work. Since Seattle has generally very mild weather, it doesn’t cost much to run the air conditioner but on the other hand, it means my house is a happy 68 degrees* all year round.
Instead of adding an air conditioner, what we really did was install a heat pump. Simply put, a heat pump uses a little bit of energy to move heat from one location to another. In the summer, we use it to move heat from the inside of the house to the outside, in the winter, we move heat from the outside to the inside. If you want to know more about how they work, How Stuff Works has a very detailed explanation.
In addition to being able to cool in the summer, the heat pump has some other great properties: It’s inexpensive to run, it produces a nice mild heat in the winter as opposed to “bursting” high heat the way a furnace does, and, it’s “greener” than a conventional gas furnace.
Because they heat in the winter by pulling heat from the outside, they stop being efficient once the temperature outside gets too cold, you still need to pair it with a supplemental heat source. In my house we use the existing gas furnace, if you didn’t already have a gas furnace, you can add electric heat elements to the heat pump. The downside to the electric heat elements, is that you lose the efficiency when they turn on.
In my house the gas heat is set to turn on around 35 degrees. The good news is, that doesn’t happen all that often around here:
As you can see, the average low in this city never drops below 37. It’s only on the occasional cold nights that my furnace turns on. In the summer, we’re never really cooling all that much, relative to the outside temp so it runs pretty efficiently too. On the really hot days, we love having it!
A lot of people ask how much it costs to run, this is really hard to say since it isn’t separated on my electric bill. My entire electric bill for my house is around $80-$120 per month depending on whether or not I’m on winter rates, summer rates, and what time of the year it is (Fall and Spring are best for me). Of course, this covers a whole lot more than jut the heat pump, computers, lights, etc… on roughly 3200 sq. ft. of home.
So, we love our heat pump, the AC is great in the summer, we love how it heats in the winter, but is it worth the cost? It depends… In our case, we had a perfectly working furnace and while I believe AC is important, it’s definitely not necessary. Further, the heat pump isn’t so efficient that it’ll pay for itself over it’s lifetime when compared to keeping my gas furnace. However, if you’re already set on buying an air conditioner, buying a heat pump instead is only about $1,000 more and you will make up that cost over it’s lifetime. Definitely, if I were doing new construction, I would install a heat pump over any other source.
In addition to whole house heat pumps, there’s another type on the market: Ductless Heat Pumps. Ductless heat pumps have been around for over 40 years are very popular in Europe and Asia. These things are very efficient and work on a room by room basis. Seattle is tripping over itself to give people money to install them (http://www.ci.seattle.wa.us/light/Conserve/dhp/).
* A note on the house temp. I like the house cold, my wife doesn’t. For some reason this is the only argument I’ve ever been able to win. It also means that she wears a hoodie in August when we’re in our basement.