Staying happy in the hot weather- without air conditioning

It's a hot week here in Ontario, and quite a few folks have instinctively fired up the air conditioners to compensate.

Before you turn on that power-hungry, money-sucking piece of machinery, though, consider trying some cheaper and less energy-intensive ways to keep comfortable around  the house in the hot weather. And, if you do end up needing the AC, don't let it pick your wallet dry.

(I'll assume, where costs are mentioned, that we pay 15 cents a kilowatt hour for electricity- a realistic average in Ontario. Scale accordingly if you live elsewhere.)

Summary (TL;DR)

I'll start with the summary, for those who don't want to read all the details.

  • Use fans.
  • Open all the windows, unless it's too hot for you in the outdoor shade.
  • Dress for the weather (light fabrics, no more than necessary).
  • Set the thermostat as warm as you're comfortable with in your new wardrobe.
  • Program the thermostat to let the house heat up during the day and cool down only when you need it to.
  • Enjoy the water if you have access to it.

Keep the air moving

Moving air feels cooler than still air- it's hard for your body to give up heat to the air when the air isn't taking that heat away with it. A good ceiling fan makes a room feel 2º to 3º C cooler than it really is. Run it in the downward-blowing direction for summer cooling.

Smaller, portable fans have much the same effect, over a smaller area. Typical fans only draw about 50 to 80 watts at full power, or 1.2 to 1.9 kWh/day. Cost: About 10 cents per fan per day in typical use, or possibly as much as 30 cents per day if you run it full speed 24/7.

Unless the outdoor temperature- in the shade with a breeze- is hotter than you want the house, you can get plenty of free cooling simply by opening windows. Cost: Free.

Get Wet

Swimming is one of the best ways to keep cool. Not many of us have our own backyard pools, but there are plenty of public pools around- or, better yet, public rivers, lakes and beaches.

Going for a swim is not always a feasible option, but it's a very good one if it's available.

Program that thermostat

Air conditioner running costs scale with the square of the temperature difference between indoors and outdoors. If it's 30º C outside, it'll cost you four times as much to chill the house to 22º as it would to cool it to 26º. Savings: \$5 a day for this particular example, if you're spending $200 a month to run the air conditioner down to 22º (pretty typical for a reasonably well built 1500 sq.ft. house in my district).

You can also save energy (and money) by letting the house warm up while you're not there. The colder the inside of the house is, the faster heat will flow into it through the windows, walls and air leaks. Letting it warm up while you're at work, then having the thermostat bring the AC back on in time for you to get home in the evening, can easily represent a 30% or better reduction in the average cost of cooling the house.

(Now and then, I see misinformation going around about "but you use more energy to cool the house back down than to keep it cold all day". Bullcrap. The physics, the math and real-world trials all say the exact opposite: the AC will always take more energy to maintain a 10º differential for eight hours than it will take to do nothing for seven hours and then pump heat back out for an hour to recover the 10º differential.)

Do you really need it so cold?

(Or, are you dressed for winter even though it's summer?)

Our natural body core temperature is 37º C, and most of us in temperate climates tend to select clothing that keeps the air temperature adjacent to our bodies about 10º C below our core temperature. That's fine in winter when we can bundle up as much as we like, but it gets pretty expensive to maintain winter-like temperatures if we want to wear cold-weather clothing year-round.

A house does not need to be chilled in July to the same temperature to which it is heated in February. Just switching from medium-heavy fabrics and long sleeves to light fabrics and short or no sleeves will, for many people, bring the "ideal" comfortable temperature up by about four degrees. (Recall from our earlier example that four degrees was worth \$5 a day; the new wardrobe pays for itself in less than a month.)

In other words: If, when you get home from work, you ditch the business attire in favour of shorts or a sarong (or nothing), you can set the thermostat in the 25º-28º C range and, with the help of a fan or two, be just as comfortable as you are at 21º-22º with your winter clothes. Savings: \$500-\$700 a summer for our relatively small and efficient townhouse.

On a business note: Theatres and chain restaurants are notorious for making us wear coats in July. Seriously, guys, cut that out already.

Take care of your equipment

We have an air conditioner. We rarely use it. Open windows, fans and appropriate attire mean that we can get by quite comfortably without the AC on all but the hottest summer days.

If we do have to fire up the AC, though, we don't want it to use any more energy than it has to. To keep the thing running in a reasonably efficient manner, it's a good idea to:

  • Clean out the leaves and debris from around it, and trim back any shrubs that might interfere with the airflow through it.
  • Check the refrigerant lines periodically for signs of corrosion or damage that could indicate a refrigerant leak. (If it's low on refrigerant, it'll suck up plenty of power while doing very little useful work.)
  • Have the refrigerant system inspected every few years by a properly trained technican.




Lower temperature?

Matthew's picture

I think you have your signs flipped, Andy. Lowering the temperature of an AC means it'll cost more- a lot more- to run it.

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