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Keep your home's biggest energy hog on a leash

Every summer the heat and humidity drives homeowners to turn up their air conditioners. If you've got an older unit, maybe it's time to think about replacing it with a new, more energy-efficient one.

Older air conditioners - both central and room - use 30- to 70-per cent more electricity than newer energy-efficient models, driving up peak demand and costing you more. In addition, older units can corrode or rust, leading to refrigerants, HCFCs and CFCs leaking and causing environmental damage and pollution. Air conditioners contain refrigerants like freon, that create the cooling effect. These are ozone-depleting substances and have global restrictions to ensure they are not released into the atmosphere.

BIGGER ISN'T ALWAYS BETTER

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Window and portable units are effective for cooling small spaces, and cost a lot less than central AC, which cools the entire home.

The size of the air conditioning unit you need is entirely dependent on your home. Contractors bidding on central AC installation jobs often incorrectly estimate the tonnage needed. Some HVAC contractors over-estimate their clients' need to make absolutely sure their client has "plenty of cooling capacity," or sometimes simply to sell whatever unit they happen to have sitting on the truck or back at the shop.

The fact is, bigger is not better. An AC unit that's too big is a waste of money to purchase, inefficient to operate, and isn't comfortable. An oversized unit will turn on and off more often, which is annoying and wasteful. So how do you make sure you don't get sold more cooling capacity than you should have?

Make sure your HVAC contractor performs a load calculation using industry-recognized methods, to determine the proper size unit. It's important to take more than just household square footage into account. It's total home air volume that counts. The calculation also needs to take into account local climate conditions, and conditions unique to the house - such as the number of south-facing windows.

Remember, too, that newer houses are more energy-efficient. They have better insulation, quality of windows and greater air tightness, which all greatly affect the amount of cooling power you need.

ARE DUCTS BEING CHECKED?

There should be enough ducts, and they should carry enough air to ensure an adequate supply of cool air to every room - and, just as important, to ensure enough warm air gets back to the air conditioner. Also, the ducts should be as air tight as possible.

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The ducts should flow through the conditioned space in your house. If they go through the attic, they should be insulated.

EFFICIENCY IS IMPORTANT

Once you figure out how big an AC unit you need, you'll want to get the most efficient unit you can. This is measured in something called SEER - Seasonal Energy Efficiency Rating. The higher the number, the more energy efficient the unit is.

Old units might have a SEER of 5. You want to go as high as you can - 16 or 18 is great. A SEER 10 will use half the electricity of a SEER 5 unit, and you'll pay for the price difference in energy savings in a few years.

SAVE ENERGY

Air conditioners are one of the biggest consumers of energy in your home, so you want to make sure yours is the most energy-efficient it can be. But even a very high-efficiency air conditioner will perform as badly as an inefficient one if it isn't installed correctly.

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TIPS:

Keep your blinds closed to avoid passive solar heating that will make your AC work harder.

Close your windows and doors when the AC is on.

Do laundry and run dishwashers - which create heat - in the evening when it's cooler to avoid peak hours.

Make sure the condensing unit of your central AC is placed where it will be shaded from the sun.

Keep the outdoor condensing unit clear of leaves and debris it will cause the unit to work extra hard and wear out sooner. Make sure there is enough space around the outdoor unit to avoid airflow restriction through the coils. Keep landscaping away from the AC unit.

Try to place the condenser in a place that won't disturb you or your neighbours - they can be noisy.

Use a programmable thermostat and set it to turn on your AC before you come home, so you're saving energy while you're at work during the day.

Mike Holmes is the host of Holmes on Homes on HGTV. For more information, go to http://www.holmesonhomes.com

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