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Is daylight saving saving the planet? Maybe, just a little bit.

Australia has once again entered daylight saving time, and because not all states observe daylight saving it has moved Australia from three to five time zones. This is a pretty big impost when you are trying to do business interstate. Why do we have daylight saving and where did it come from?


Benjamin Franklin first proposed daylight saving

Yes, ‘that’ Benjamin Franklin, the scientist and one of the founding fathers of the United States. In later life he had the position of ‘American delegate in Paris’. In 1784 he composed an essay ‘An Economic Project” whereby he proposed that Parisians could save about 64 million pounds (around 30,000 Tons) of wax and tallow per year by moving the clocks forward. The saving was simply because they wouldn’t have to burn their candles as long into the evening.

The idea wasn’t embraced for over 100 years. Germany was the first country to adopt daylight saving, soon followed by England in 1916. Daylight saving was created to save energy, not for twilight strolls.

Australia adopted daylight saving in the first and second world wars as an energy saving measure. Tasmania re-introduced daylight saving to reduce electricity demand when they were in the grips of a severe drought in 1967, which threatened their hydro power supply. The Tasmanians liked the longer summer evenings and twilight strolls so much that they convinced the rest of the country to give it a go in 1971 (except Western Australia and Northern Territory).
After the 1971 trial, New South Wales, Victoria and South Australia stuck with daylight saving, Queensland has trialled it (1989-1992) before voting it down in a referendum. Similarly, Western Australia trialled daylight saving (2006-2009) before voting it down. So now we have five time zones in the summer months.

The initial rationale for daylight saving is all about saving energy. Specifically energy spent on evening lighting. However our energy consumption profiles have changed dramatically since the idea was proposed. I was wondering if daylight saving might actually consume more energy these days. My rationale is that with the proliferation of home air conditioners, the extra hour at home during the heat of the day may result in more use of residential air conditioners. This seems like a pretty easy hypothesis to test.


The Queensland – New South Wales natural experiment in daylight saving energy use

We have the perfect natural experiment to demonstrate the energy saving potential of daylight saving. Queensland does not have daylight saving but New South Wales does. These two states meet at Tweed Heads (southern end of the Gold Coast). I have tracked down electricity use data from the Australian Bureau of Statistics. I have tallied up the total electricity use from non-generating (i.e. no solar panels) residential connections for Queensland just north of the border (Coolangatta, Currumbin, Currumbin Waters, Elanora and Palm Beach). For northern New South Wales I have tallied up Kingscliff, Tweed Heads and Tweed Heads South electricity use. The population of these areas is pretty comparable (50,096 for the Coolangatta region and 55,174 for the Tweed Heads region – source ABS ).

A caveat here is that the data is electricity use only, and doesn’t include gas. The area is serviced by natural gas, so I am making the bold assumption that the relative energy contribution from gas vs electricity is the same across the region.

Unfortunately the ABS energy use data is presented as calendar year totals, so we cannot compare just the daylight saving months. Given that the climate is the same for the region, the building construction the same, the electricity price is about the same and the demographics by my reckoning should be pretty similar then the annual electricity use comparison should reflect the time zone difference.

Figure 1 shows the per customer energy use (mean of median annual use per connection for the suburbs) for about 10km either side of the Tweed River.

That is a really massive difference. I really cannot believe that daylight saving reduces electricity consumption by more than 10 % (or 600-1200kWh). By comparison, France estimates a saving of around 17kWh per household due to daylight savings. Other studies have suggested that daylight saving could account for plus or minus about 1% in energy saving/cost.

Perhaps the difference relates to a few big industries in the Coolangatta region, however we are considering the median customer use (rather than mean), to avoid the skew from a few big users.

Perhaps the household demographics are dramatically different. If we simply divide the number of meters by the population in each area (2011 census) we get 2.05 people per meter for the Coolangatta region and 2.31 for the Tweed region. So on a per person basis, the difference between the regions is even greater. I presume that there is some inconsistency in methodology between the regions for reporting the electricity use.


Figure 1: Median customer energy use in the Tweed River area (boxes show % electricity saving due to daylight saving) data source – ABS.

To think about it the way Benjamin Franklin did, daylight saving will reduce the amount of energy required for lighting. You still need to cook, wash and vacuum. Sustainability Victoria estimate that lighting is about 11% of your energy use. If you reduce your lights from say four hours per day to three due to daylight saving, we might expect a maximum energy saving due to daylight saving of 2.75%. And that is if you are not tempted to turn on the air conditioner. So these >10% savings in energy from the Tweed region (Figure 1) are something more than just daylight saving but perhaps a deeper earth loving conservation philosophy that is created as you pass the border. Or perhaps some inconsistency in data reporting…
So this has been a slightly underwhelming little data analysis exercise, but it reminds us of an important lesson. The truth may be in the data, but only if you have confidence in the data. If the results of your analysis don’t make sense, there is probably something else going on.

Regardless of the energy saving, it is lovely to have long twilight summer evenings in the southern states.

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