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Week Twenty - Smarter Cooling

Save 8 kilograms CO2e per person per year

· Weekly experiments

My preschooler

- Okay, you two, stop quarrelling.


- Sorry. Daddy and I aren't coping with the heat. At least we only argued for a week, not twenty years.

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It's Australia Day and I'm angry.

Heatwaves, bushfires and blackouts blitz the nation. Rob and I have been sniping at each other all week. Fortunately, the four-year-old is the voice of reason in our house. Unfortunately, Australia's been quarrelling for two decades over climate change with no end in sight. Can I send in my preschooler to sort out their House, too?

Smarter cooling

Around half of Australian households use reverse cycle air conditioning, 14% use evaporative cooling and 10% use refrigerated-only cooling. One-quarter of Australia's households have no cooling system at all, including 4% of Northern Territorians who must be frying.

Our evaporative cooler works well in Canberra's dry climate [NOTE: Bushfire smoke in Canberra means we can no longer use evaporative cooling on the hottest days. I would not recommend these if you live in a smoke-prone zone.] But we haven't been using it properly. We run it on manual and dial it up or down as the whim takes us, which is reputedly the least efficient way to do it. For this week's experiment, I busted out the manual and learned how to program it properly. I pushed the limits on how little we could use it and came up with a new set point for comfort. I also spent half an hour on the phone with the manufacturer, who utterly failed to answer any of my questions about what the different settings mean and how to use the system more efficiently. Once again, I'm shocked by an industry's basic lack of literacy when it comes to energy and emissions.

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This Canberra pub uses umbrellas & misters to beat the heat, but in forty degrees, the punters aren't biting.

How much CO2e did I save?

Like the NEG, this week's experiment was a bit of a failure. By using automatic rather than manual and dialling down to use less power, we saved - wait for it - a kilogram of carbon dioxide and equivalent emissions (CO2e). During the twelve weeks of summer, that would save twelve kilograms (4 kilograms per person).

I can't quite believe my data. Our house definitely felt less cool this week, so where are our savings? A simple weather comparison shows the temperature last week and this week is comparable, so that's not the reason. My family was home more due to the long weekend, but I still expected a bigger drop in power use.

I took readings for total household electricity use, not my evaporate cooler alone, so it's possible we used less on cooling but another appliance took over. The fridge has been making worrying noises in the heatwave. We'll stick with our automatic higher-temperature settings on the cooler and watch next week's experiment to see if the data shifts.

It's hard to give a figure for what the 'average' Australian might save. The average 3 bedroom household in my suburb uses around 1292 kilowatt hours over summer, emitting around 1,189 kilograms of CO2e. I'll assume this average house uses 40% of its electricity for cooling. Industry and governments make bold claims that you can save 5% - 10% for each degree shifted up in summer. Let's stick with a 5% saving for setting the cooler to a higher temperature and using it more efficiently. This means the 'average' 3 person house will save 24 kilograms of CO2e over summer (8 kilograms per person). If it makes you less comfortable, it's hardly worth doing.

The above only applies to a very rough 'average' for a house using 1292 kilowatt hours of electricity over summer. If you're a superconsumer running a large, poorly insulated house cooled to a chilly 22 degrees, you're certainly emitting more and you could easily make bigger savings.

Change the grid

This experiment left me angry. Unlike other areas of consumption, it's hard for individuals to make much difference by using less electricity to cool the house. But the government knows it can slash grid emissions by 80% with a policy change because some states have already done it. Tasmania generates 0.22 kilograms CO2e per kilowatt hour of power, where coal-loving Victoria generates 1.16 kilograms CO2e (see Table 41 NGA 2018). If I lived in Tassie, I'd save 900 kilograms CO2e each year in summer alone using exactly the same power I use now. No sweat.

Australia has solar, wind, hydro and the rest. Yet we're still hooked on coal, even though it's expensive, unreliable and it's cooking the climate. On our day of national celebration, after twenty years of squabbling, can't we come together and get this right?

Tips for smarter cooling

If you want to be efficient with your cooler, don't fall for the myths.

- Don't dial down to cool faster. When you walk into a hot room, don't dial down the AC to a lower temperature than you need. It won't cool the house faster and it will waste energy when you forget to turn it back up.

- Don't leave it on to keep the house cool. Don't keep your AC on all day if everyone's out. It isn't more efficient to keep the house at a low set temperature, it's more efficient to switch it off. You can turn it back on when you get in or program it so it switches on fifteen minutes before you arrive home.

- Don't set the temperature too low. The inside / outside differential is key. On hotter days, you can handle a hotter indoor environment. On any day, you'll likely find everyone adjusts to a higher temperature once they're used to it.

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If you want less of this, our grid needs to pump out less CO2e.


Spreadsheet calculations, notes and data sources in the 'Notes' section, Week Twenty.