When our home central air conditioner failed last year, I decided to experiment with an alternative approach to cooling our house. We have seen our electricity costs soar in Ontario over the last several years, so minimizing air conditioner use seemed a worthwhile exercise.
Even when our air conditioner had worked well, we had always turned it off when the weather was mild, say 25C (77F) or cooler. We preferred the gentle summer breezes (whether warm or cool) during the day and the cool breezes at night. But now that our air conditioner was no more, we had to cope with the warmer weather as best we could, even on the hottest of days
Damned Government Incompetence
As an aside, electricity prices in Ontario are a great advertisement for government incompetence, indifference and corruption. The price of electricity has skyrocketed so that the unit cost of hydro in Ontario at peak times is now 3.74 times what is was 13 years ago. Ontario Hydro might counter that the off-peak price is only 1.86 times what it was, but that’s hardly something to celebrate and is little consolation for us poor rate payers.
Cooling Without Hydro
Because we’re in Canada we usually have cool evenings even on the hottest days, giving us a free alternative to our defunct air conditioner and a means to reduce our hydro bill. The kernel of the solution is simple: open all the windows at night, closing them and the window coverings during the day. In other words, cool down the house at night and insulate it during the day. Obvious, right? I think so but, then again, none of our neighbours seem to use this simple approach to cost savings. We hear their air conditioner compressors running even on the coolest nights of the summer. Why, I wonder, would anyone want to run an air conditioner when the evening temperature is 12C (54F)? Besides, aside from the monetary and environmental savings associated with the open-window approach, I find the cool nighttime breeze of fresh air preferable to the stale recirculated air from the air conditioner.
“So what happened with the experiment?” you might ask.
The results were really quite amazing. We discovered that so long as the evening temperature was 19C (66F) or lower, and the daytime temperature was 31C (88F) or lower, we could stay very comfortable in the house without our air conditioner. When the evening or daytime temperatures exceeded these limits we were still comfortable for most of the day, though there could be several hours in the evening where we decided to turn on a secondary conditioner. The primary purpose of this air conditioner was to dehumidify the air, rather than to lower the household temperature. A dehumidifier may have worked just as well.
Temperature vs Humidity
The reason that I am focusing on dehumidification is that it was a relatively fast process, reducing the household humidity to comfortable levels within about 45 minutes. Cooling on the other had was a relatively slow process, requiring about an hour to reduce the household temperature by 0.5C (0.9F). The reason for the difference seems clear. Through the hot day, the house itself heated up and stored the heat (in the walls, floors, furniture). The humidity, however, was really just airborne. I suppose it’s possible some of the water vapour was absorbed into materials like fabric and carpeting, but because most of the humidity was in the air it was removed rather quickly.
Cooking the House
There is one detail of our setup that makes our situation somewhat unique, but also means that others may fare even better than we did. The back of our house faces South, with very large windows that are virtually unobstructed by trees or other blockages. We therefore have a serious problem with the solar heating of our home on sunny days. Although the South-facing windows are covered with wood shutters, blocking out the sun quite well during the day, the windows still let through significant heat when it’s sunny. The South side of the house is very well cooked after a full day in the sun.
If we operated our air conditioner like our neighbours, meaning that we sealed the windows and air conditioned the house every day for the months of June, July and August, I estimate that our air conditioner compressor would have run for approximately 1250 hours over these months. If we fixed our air conditioner, but avoided using it at most times (ie. we opened our the windows at night and sealed them during the day, but used the air conditioner liberally to keep the house temperature and humidity at a reasonable level), I estimate that our compressor would have run for about 150 hours over the summer. That’s a savings of 88%. In the case of our 3 ton air conditioner, the 1100 hours we didn’t run it would have saved us about $400 in electricity charges for the summer. That may not sound like a lot, but this summer wasn’t particularly hot. And, besides, we’re in Ontario, not Florida. Heat really isn’t supposed to be a significant problem here. We also didn’t lose anything by opening our windows at night. And we gained the fresh air.
Even once we eventually fix our air conditioner, we’ve decided to stick with our current money-saving approach. It works. It’s cheap. And we are happier with our windows open at night.
Of course this approach wouldn’t work in many areas, including the US South. But it may well work to some degree in many other locales. In some desert environments, with hot days and cool nights, the benefit may even be greater than ours.
The point of writing this summary is to show how easy it is to save money with a little thought (or, in this case, a timely opportunity). I have used many other such approaches, some of which I also hope to eventually share in this blog.
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