Cool advice: the pros and cons of air con
Avoid air conditioning to save money if you can (or use it strategically)
When a heat wave hits, it's not difficult to find portable air conditioners at your local big box retailer. And after a sweaty night tossing and turning in your bed, an air conditioner can look about as enticing as a salmon to a grizzly.
A recent report by the International Energy Agency predicts that the number of air conditioners across the world will increase from about 1.6 billion units today to 5.6 billion by the year 2050. And a new BC Hydro report [PDF, 432 KB] finds that the number of B.C. homes with some type of air conditioning has increased from 10% in 2001 to 34% in 2017.
Before you take the plunge, or even if you've already forked out for air conditioning, consider the advice of Pat Mathot. Not only has he done a deep dive into cooling strategies as a manager with BC Hydro's conservation and energy management group, he's done a whole lot of experimentation in his own home.
Summer comfort starts with not letting your house warm up
At BC Hydro, we talk an awful lot about stuff like solar gain. In layperson's terms, it's really about the sun bombarding your home with heat, often turning your home into a sauna.
If you're really on the ball, you'll plant a deciduous shade tree – one that sprouts leaves to block the sun when you need it, and drop those leaves in time to warm your home in winter – on the south or west side of your home. But we can't all do that, especially those of us who live in apartments. So the priority turns to strategic use of windows and window coverings.
"Typically speaking, most of us come from an experience where when it's hot outside, you open up the windows for fresh air," says Mathot. "But if the outside temperature is considerably warmer, it's about as logical as opening windows during the extreme of winter cold. In summer, you're just going to lose the cool in your house when you open up your windows."
Keep windows closed whenever the temperature outside is warmer than it is in your home, says Mathot, who also stresses the importance of drawing blinds and other window coverings to block the sun's entry. In his case, he's drawing the blinds – which can cut down heat entering the home by up to 65% – before he goes to bed. "In our house, we turn the blinds down on the east side of the house before we go to bed, because we know that at 5 a.m., here comes the sun," he says, resisting the temptation to break into the Beatles song. "That's like two, to two and a half hours that the sun would have been bashing into our home and heating it up and I would have been sleeping through it."
Still too hot? Use cooling fans to create air flow
On a recent summery day in May, it was already 18°C when Mathot drove away from his home at 7:30 a.m. When he got home in the evening, it was time to get the air flowing. Once the temperature outside is lower than it is inside the home, he opens windows and uses floor fans – which use far less electricity than air conditioners – to help draw warm air out, and cool air in, to his home.
"We put fans upstairs to blow the warm air out the window, and a fan at the base of the stairs to move the cooler air up from downstairs," he says. "Ninety per cent of the time that works, but you can't open the windows until the air outside gets cooler than it is in your home."
Here are estimated costs of using three different ways to cool your home, based on BC Hydro data for average daily use by each type of device:
- Two 75-watt floor fans running an average of 4.7 hours a day over three months will cost you about $7 in electricity charges.
- An ENERGY STAR®-rated room air conditioner at six hours a day would cost you about $24 over those three months.
- A central air conditioning system operating 9.4 hours a day would use an estimated $323 in electricity over two months.
If your place turns into a sauna only a few weeks a year, floor fans may be enough to ensure you're still comfortable and can sleep at night. Even earlier in the evening, the moving air produced by a fan feels cool on the skin, even if it's not actually cooling the air.
Got a bigger cooling challenge that requires air conditioning? Read on.
Think you need air conditioning? Buy ENERGY STAR, and think small
In certain parts of B.C., central air conditioning may be the only way to keep a home cool and comfortable. But if you were to run that whole-home air conditioning 12 hours a day over a month, it could cost you more than $130 in electricity.
Mathot says a lot more British Columbians are opting for some type of air conditioning for a variety of reasons. Our summers have been hotter the last few years, many apartments are tough to cool down, and a lot more people are moving into warmer areas away from the water.
"It's a lot hotter in the Fraser Valley than it is near the ocean," he says. "I was in the valley in Abbotsford last weekend and it was 30°C there. I went home to my place, which is close to the water, and it was 24."
Apartments in B.C.'s Lower Mainland are often glass-walled with lots of exposure to the sun and – with no outdoor-facing back door – no way to create air flow through the home. Many apartment dwellers are turning to portable air conditioners to cool their homes.
"Portable room air conditioners are going to be the most efficient, if you just need them for sleeping or whatever," says Mathot. "You want to make sure the door is closed to keep the room cool. Do you want to pre-cool the room before you go to bed? Do you need to keep it running all night? Typically on most nights, the temperature comes down again outside, so you can eventually open the windows and turn the air conditioner off."
How efficient is that air conditioner? As you shop for one, look for its efficiency rating, known broadly as SEER but also in Canada as EER. The higher the rating, the more efficient.
- For room air conditioners, the EER ranges from a low of 9.8 (least efficient) to a high of 12 (most efficient), and look for the ENERGY STAR label.
- Central air conditioners have an EER range of between 13 and 24.5
- Ductless central air conditioners have an EER range of 13 and 26.
Another popular option for cooling is a heat pump, but while a heat pump operates just like an air conditioner, most are optimized for heat and are therefore slightly less efficient at cooling than a dedicated air conditioning unit.
For most of us, 24 or 25°C is comfortable, so don't overdo it
For years, BC Hydro has been recommending that when using air conditioning, set the temperature to 24 or 25°C. Mathot couldn't agree more.
"If you use your heat pump to warm your house to 20°C in the winter, you shouldn't be using it to cool your house to 20°C in the summer," he says. "It should be significantly warmer, because to our bodies, 24 or 25 degrees isn't horrible."
It's also a myth that you need to maintain that comfortable temperature while you're away at work or out of the home for longer periods. Adjusting or programming the thermostat 2 to 3°C higher will still enable you to fairly quickly cool your home to the desired temperature when you return.
Using a room or portable air conditioner? Because you have the ability to quickly cool a room for sleep or other activities, consider shutting it off during the day. It won't rob you of the comfort you're looking for, and you'll save money on your energy bills.