Don't be cool, be super-cool

Pre-cool your home overnight before a hot day, and you can save energy and wear & tear on your air conditioning system

Don't be cool, be super-cool

If you have air-conditioning, you are one of the lucky ones through those hot summer days — at least until the electricity bill arrives.

Don't let your summer energy bills get you down. Supercooling is a strategy that could help you keep your home cool and your bills low during the hottest summer days.

What is supercooling?

Most people have their cooling system set to run during the hot part of the day and then turn off or go to a lower setting during the cooler hours of the night. This means the AC system switches on when the house is already warm, so it has to work hard (and will use a lot of expensive energy) to cool things down.

Supercooling or pre-cooling flips this approach on its head, by cooling your house before the hot day begins.

This strategy is suitable only for houses under time-of-use electricity tariffs. It's most viable in hot, dry climates and works best for homes with good thermal efficiency.

Next time a hot day is forecast, try cranking up your air-conditioner overnight to get your house down as low as about 15 degrees. As temperatures rise the next day, your house will start off nice and cold — and can stay that way for a long time, so you can get away with running your air conditioning at low power during the hot parts of the day, and maybe you won't need to use it at all.

Supercooling has two key potential advantages:

  • Lower energy costs: If your utility plan has different rates for peak and off-peak times, you can save money because you’re running your power-greedy airconditioning system during off-peak times when rates will be lower, and minimising usage during peak times
  • Less wear and tear: If your house is already hot when you turn on your air conditioner, the compressor, fan, and other components will have to work harder to cool the place down. Running it at night when the ambient temperature is lower means less wear and tear, and your system may last longer and require less maintenance.

It may sound far-fetched, but the evidence is that it really can work both to save you money and to spare your equipment.

Keep your home supercooled

Supercooling works best for homes that have good thermal efficiency — so the cool can last well into the day — but even then, you need to adopt some simple best practices to maximise the benefit:

  • Variable rates: You'll need to be on a time-of-use tariff for this strategy to make sense, because the idea is to run your AC runs at night when power is cheaper, so you can run it less (or not at all) during the day when it’s more expensive.
  • Set your thermostat: Set your the desired maximum temperature to ensure the most efficient operation. Your AC will kick in automatically if it needs to later in the day.
  • Close the windows and blinds: Keep all your windows and internal doors closed and keep the shades or blinds down to maximise thermal efficiency.
  • Don't create heat: You're trying to keep the house cool, so don't heat things up from the inside by using the oven or any other heat generating appliances like the dishwasher.
  • Be chill: Supercooling means your house will get cold at night. You might feel silly rugging up for winter during the height of a heat wave, but you'll be glad when your electric bill is low.

Supercooling requires discipline and planning, but it has the potential to lower your electric bill while keeping your house at a comfortable temperature all day.

Your mileage may vary depending on your home’s characteristics (and your tolerance for freezing at night), but if your energy bills are shocking, it’s worth a try.

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