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Hot summer nights, and cold winter evenings: how to be comfortable and save money all year long

Every summer, the number of Australian homes equipped with air conditioners goes up and up. Recent statistics show that 74% of Australian homes – 6.6 million so far – have some form of air conditioning. This stands to reason because our summers are becoming hotter and hotter while we increasingly demand constant comfort.

At the same time, air conditioners drive up electricity demand, straining the electricity network. So what are you to do if you want to enjoy a guilt-free, full night’s sleep?

And then there’s the question of heating in winter: cast your mind back to those freezing days and nights, which occur especially in places like Victoria, Canberra, and Tasmania - but in fact happen in all of the other states too.

If you make the right decisions when buying an air conditioner this summer, you can enjoy even greater benefits over the long and dreary winter months to come.

Heat pumps for winter and summer

Previously I’ve reported that heating your Australian home with a modern reverse-cycle air conditioner - also known as an air-source heat pump - can be far cheaper than heating your house by burning gas. Heat pumps can work both ways: cooling and heating when required.

When used in winter for space-heating, air-source heat pumps harvest renewable energy from the heat contained in the air outside your home. For every one unit of electricity they use, they provide up to 4.8 units of free heat. This makes them incredibly efficient.

But with the arrival of some record-setting hot nights, it is easy for the hot-and-bothered air-conditioner buyer to lose sight of the bigger picture. So keep in mind, buying a reverse-cycle air conditioner doesn’t cost much more than one that only cools, in some cases as little as A$50 more.

And as the University of Melbourne Energy Institute and the Alternative Technology Association has found, come next winter, using your reverse-cycle air conditioner instead of gas can reduce heating costs by up to A$658 per year in a large Melbourne home or even up to A$1,733 per year in a large Canberra home. So spending a bit more for a dual-purpose cooling-and-heating device is clearly worth it.

Infrared camera (thermal image) of wall-mounted air conditioner producing heat at 50C. Tim Forcey

Furthermore, when buying an air conditioner, select one with a large number of energy efficiency stars. It will cost around 27% less to operate a five-star-rated heat pump versus one with only three-stars. Your savings can add up to thousands of dollars over the life of the equipment. The government website Energy Rating provides a cost calculator and lists all air conditioners on the Australian market, including one device that leads the pack with an efficiency rating of seven stars.

Note that some of the larger Australian white-goods suppliers offer a limited range, with no air conditioners in their stables rated better than four stars.

Helping the grid

The operators of our electricity-supply facilities have long been concerned with how summer air conditioning strains the system. No one wants to see blackouts at the critical peak demand moment when electricity is most needed.

Fortunately, no electricity-demand records have been set across any eastern-Australian state since 2011, even though the Australian economy and population has continued to grow. Why not?

The annual consumption of grid-supplied electricity declined for a number of years since 2009 (see the figure below), mainly as a result of energy efficiency programs including the deployment of higher-efficiency appliances: air conditioners, televisions, refrigerators, lighting, and so on.

Australia GDP compared with consumption of grid-supplied electricity in eastern Australia. 'Five years of declining consumption of grid-supplied electricity in eastern Australia, causes and consequences'. Sandiford, M. et al., The Electricity Journal

Rooftop solar power on 1.4 million Australian homes has also delayed the time of day at which peak demand occurs, easing the pressure on the electricity grid.

Finally, over the last few years, we have been fortunate that periods of very hot weather have not aligned with weekdays after the summer holiday period.

That said, the increasing use of air conditioners in summer, in concert with some very hot weather might someday cause electricity demand to exceed the capabilities of the supply system somewhere in a central business district, suburb, or regional area. To reduce demand on the system, those in the market for an air conditioner can make sure they buy the most efficient unit their budget allows, and also work to reduce their electricity demand on hot summer evenings in other ways.

Don’t feel guilty about your desire to sleep well on a hot summer night. Come next winter, rest assured when you are cheaply and comfortably heating your home with your efficient electric heat pump.

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