Friday, November 28, 2014

Energy efficient behaviour pays


Investing in energy efficient buildings is a powerful way to save energy, but ultimately the occupants' behaviour is what determines power use. Without spending any additional money, you can reduce your consumption right now by changing your behaviour.


I work as an energy efficiency consultant. Generally, this involves finding investments that can be made (eg. LED lighting, better insulation, variable-speed-drives) that will result in decreased energy consumption. This works well, and there are generally good opportunities for people and organisations to make targeted investments in energy efficiency with good economic returns. However, it is easy to be blind to the most significant effect on energy consumption: human behaviour. Let me illustrate this by way of an example.

My family and I lived in Brisbane for almost three years, arriving in late 2010. We owned our home, and made some energy efficiency investments in it (solar PV, solar hot water, better lighting, blinds). Once these measures were completed, we were using about 5 - 6 kWh/day. When it came time for us to leave Brisbane, the real-estate market was poor, so we decided to rent out the house rather then sell it. We did this for a year and, because of the way the feed-in tariff (FiT) operates in Queensland, we kept control of the electricity supply and were reimbursed by our tenants (had we transferred the supply to them, they would have lost the solar PV FiT). Thus, we were able to see their consumption on a quarterly basis. What was immediately apparent was that their consumption was much higher than ours -- generally it was 2 - 3 times higher. Where we were using 5 - 6 kWh/day, they were using 14 to 18 kWh/day -- in the same house. Clearly, their appliances were different, which could account for part of this, but the majority of this difference I attribute to behavioural differences [1].

What this shows is that simple behavioural change can be hugely significant. Simple behaviours like these have a huge affect on household power consumption:

  • whether the oven is used in batches to cook a lot at once, or if it often turned on for only one small dish
  • whether appliances are turned off at the wall when not in use
  • whether there are many energy-hungry appliances (eg. large TVs)
  • when and how air-conditioning is used
  • whether lights are turned off
  • whether hot food is routinely put in the fridge without pre-cooling
  • how hot water is used
  • whether computers are left running when not used


This shows that energy efficient measures are important, but that the energy use of a building is determined in the end by its occupants. A positive way of seeing this is that you can save energy, without spending any money, merely by changing your behaviour.

[1] We were regularly washing nappies, and we also cook a lot. At that time, we had a relatively inefficient fridge -- thus we could have used a lot less also. Also, note that this house has one small through-window reverse cycle air conditioner, but is mostly not air-conditioned. Thus air-conditioning cannot account for this difference either.

This article was written by Angus Wallace, and first appeared at


  1. Hi Angus. 5-6kWh / day is a very good outcome. Incidentally, in SA, you could easily produce that much energy 365 days per year with solar PV. It would be interesting to hear a blog entry about how you are going now in SA with your usage?
    Your observation about your tenants in Brisbane is very true about human behaviour. The same is true for businesses too, in that two different people can run the same business very differently. I'm far less interested these days in what people earn, but it is what they do with what they earn which is the interesting thing.
    Incidentally, the air conditioning system which exhausts to the outside world is the most efficient arrangement. There has been a bit of discussion about portable air-conditioning units over at the Energy Matters Forum. The upshot is that the portable units which exhaust into a room both heat and cool the air at the same time, so achieve nothing.
    Cheers. Chris

  2. Hi Chris,
    Yes, at the moment we're exporting 3 kWh for every 1 kWh we draw (from a 2 kW solar PV system). I think we're using 3 - 4 kWh/day on average at the moment (though it is hard to work out exactly, because our metering doesn't measure our consumption of power that we've generated directly). I've written a blog post about our current consumption here:

    Totally agree re:business. I've come to realise that social and personal skills are much more important than technical skills as a determinant of success! (in any area)

    Regarding A/C, I think the best solution (in SA, at least, where it's dry) is evaporative (provided that plenty of clean water is available). Evaporative A/C uses about 10 - 20% of the energy of reverse-cycle -- but it doesn't work well when the weather is humid.

    But as far as reverse-cycle A/C goes, I think you're right. There are some very efficient split-systems available these days and if the external unit (condenser when operating to cool the house interior) is located sensibly (in a relatively cool place -- eg. not in the afternoon sun ;-) ) they can work reasonably well -- but still no where near as efficient as an evaporative cooler!

    Cheers, Angus


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