May 1, 2016: Counting Comfort and Costs

In last week’s Newsletter I shared the energy performance results from our second full year in the Greeny Flat. I was very happy to report that we continue to be well and truly energy positive in spite of the fact that we are now putting quite a bit of our excess energy into our Electric Car. However, as you can see from the table on our Results Page, we keep track of more than just energy production and consumption. We also monitor our water usage, comfort levels and running costs. In response to last week’s Newsletter I received the following email from a reader named Jeremy (who incidentally has developed a wonderful app for monitoring the motor, battery and charging systems for electric vehicles which you can learn more about at

Hi Andy,

I found your latest blog really interesting, particularly for a parameter in your spreadsheet that you didn’t discuss -“comfort”. Very impressive that with an outside temp range of 46.2 degrees you manged to keep the inside range down to 16.3 degrees (30.1 reduction!), well done. I think you previously said you do have a wood combustion heater to help the winter temp? However 28.7 on a 41.6 day without airconditioning is a great achievement, especially if the surrounding days were also very hot? It looks like you don’t even have a roof void in Greeny Flat, is that correct?
Mowing the grass is very satisfying knowing that the power is coming straight from our solar panels. It's quiet too!

The Greeny Flat is ‘All-Electric’, even down to the lawn mower.

Thanks Jeremy for the compliment and for reminding me to discuss the ‘Comfort’ issue. One BIG thing that I would like to point out is that we DO NOT have a wood combustion heater to help keep the house warm in winter. The house is all electric for reasons discussed here. Even the lawn mower is electric so when we say our home is ‘Energy Positive’ we can be confident that this is true. We have a very small, electric fan heater that we use occasionally when it’s a bit nippy, but otherwise the house is entirely heated by the sun and good Passive Solar Design.
Jeremy is correct that we don’t have a roof void (e.g. an attic). This is significant because a well-insulated and well-vented attic can help a lot with keeping a house cool in summer. Our roof is made of SIPS panels (similar to those used to make cool rooms) which provide very good insulation with no thermal bridging and also do an excellent job of keeping the house cool.
In regard to the ‘Comfort’ levels we have recorded on our Results Page over the last two years I would like to make note of the following (all temperatures are in degrees C):
  • The outdoor temperature has ranged from -4.6 to 41.6 while the indoor temperature has only ranged between 12.4 and 28.7. As Jeremy points out this is means that the indoor range is only about one third of the outdoor range.
  • In these readings I have ignored a period when Cintia and I were away last winter and the indoor temperature dropped down to 10.6. Because we weren’t here to operate the blinds correctly no sun was coming in during the day. What is interesting about this is that the house still didn’t go any lower than 10.6 which tells me that we made the right decision in not putting insulation under the floor slab. The constant ground temperature under our house must be around 10.6 degrees. If we had insulated the floor slab we would have been disconnected from this ‘heat sink’ and I suspect that the house would have got a lot colder when we weren’t here for the winter.
  • I find it particularly interesting to look at the average temperature figures. During the first two years, the average outdoor temperature ranged from 3 to 31 while the average indoor temperature ranged from 16 to 26. This tells me that, most of the time, the indoor temperature stayed within a pretty comfortable 10 degree range.
  • The extreme readings of 12.4 and 28.7 are not very comfortable indoor temperatures however, they only occurred for very brief periods of time. If any readers are really good with Excel spreadsheets and have some time on their hands I would be very interested to crunch the numbers to find out what the temperature ranges were for (let’s say) 90% of the time. This would eliminate the brief extremes and tell us what the comfort range was for the majority of the time. Please let me know if you would like to have a crack at this and I’ll gladly send you the spreadsheet.

Running Costs Up a Bit

Further down on the Results Page you will see a small table that shows our entire first year’s running cost for the house. Our total energy bill for the year was $257.68. I have just finished adding up our energy bills for this year and they came to $407.04. Halfway through this year we switched from AGL (because they are Australia’s biggest polluters) to Click Energy (because they offer the best Feed In Tariff for solar owners at 10c/kWh). So it’s a bit complicated to figure out exactly what has caused the increase. I need to look into this further but I suspect three possible causes:

  1. Electricity rates may have gone up, particularly the daily connection fees.
  2. After the resounding success of our first year we may well have relaxed a fair bit on our energy use habits.
  3. Adding the electric car has definitely increased our consumption over the last four months. Even though we almost always charge it directly from our solar system during the day this still incurs a cost. If we weren’t charging the car we’d be putting that energy into the grid and getting 10c/kWh from Click Energy. So it effectively costs us 10c/kWh to charge the car during the day. As discussed further here, this is still less than half the cost of running the car on petrol. So even though we are seeing an increase in our electricity bills we are still saving money through much lower petrol bills.

In Other News…

Installing Solar Panels with an Allen Key?

160501 Ikea allen key

According to this article in The Guardian, Ikea is going to start selling solar power systems in the UK. Like many people, I have a love/hate relationship with Ikea. Some of their design ideas are incredibly clever but some of their sales and marketing concepts are frustrating, not least of which is the fact that they flat pack everything to save on shipping costs and energy use which means that we poor suckers have to put their stuff together when we get it home. I’m sure you’re all familiar with their lovely little Allen Keys. Let’s hope that, when it comes to buying a solar system from Ikea, we won’t have to load it ourselves from their warehouse shelves, strap it on the roof of our Honda Jazz with a bit of string, lay it all out on the living room floor, scratch our heads over the wordless instructions and screw it all together with an allen key.


As far as I can tell, Volvo currently has NO electric vehicles in it’s range. So it seems incredibly ambitious of them to set a goal of selling one million electric vehicles by 2025. But, according to this article from Gizmag, that’s exactly what they have done and it is a clear sign that the shift to electric vehicles has well and truly taken root around the world.

“It is a deliberately ambitious target,” says Hakan Samuelsson, Volvo president and chief executive. “It is going to be a challenge, but Volvo wants to be at the forefront of this shift to electrification.”

Solar Fransisco

160501 solar fransisco

Source: Gizmag

According to this article from the San Fransisco Examiner, the city has recently passed a law requiring all new buildings less than 10 storeys high to have solar panels installed on their roofs. This is part of a major series of initiatives on the part of the city to reduce its carbon emissions and take steps to deal with climate change.

San Francisco has climate goals to achieve zero waste going to the landfill, 50 percent of all trips taken by an alternative to a private automobile such as by bus or bicycle and 100 percent of energy used from renewable energy by 2025.

Barry Hooper, the Department of Environment Green Building Coordinator, said last week “that 100 percent renewable energy depends on both development of renewable energy resources and continued improvement in energy efficiency.”

I’m very glad to read that they are looking closely at energy efficiency improvements as well as renewable energy because the two have to go hand in hand if we are to have any hope of moving to a carbon neutral economy. Personally I would like to see a requirement that all new buildings in Australia have to be energy positive. This is better than just requiring solar panels because it forces builders and developers to look at reducing energy consumption as well as producing renewable energy. I know… I’m dreamin’… but ‘if we can dream it, we can do it’.

ACTing on Climate Change

On the above point, I was impressed this week to learn that the ACT has recently won some sort of award for being the Number 1 jurisdiction in the world for action on climate change. I heard about this at an information session on the ACT’s most recent renewable energy auction which I attended on behalf of Renewable Energy Wingecarribee Pty Ltd. I’ve just done a quick search for information about the award on the internet and couldn’t find anything so I can’t give you any more detail at this point. What I can tell you is that the ACT is well ahead of schedule in its plans to switch to renewable energy. In fact it has just been announced that they have moved the goal of 100% Renewable Electricity forward from 2025 to 2020.

It is VERY important to understand that reaching 100% Renewable Electricity is a LONG way from 100% Renewable Energy or from ‘Carbon Neutral’. In order to be Carbon Neutral they will have to take into account ALL of their energy uses (gas, coal, petrol, diesel, wood, etc) AND all of their greenhouse gas emissions from other sources (such as cement production, landfill gases, farm methane, etc, etc). Suffice to say that electricity consumption accounts for only a small percentage of our total carbon emissions so the ACT still has a very long road ahead to get to their goals. Nevertheless, it’s encouraging to see that a) they have set ambitious goals for climate action and b) they are moving aggressively (and successfully) towards meeting those goals.

Let’s hope that the NSW Government and the Federal Government follow suit. I have high hopes that the upcoming election will shift the balance of power away from the climate deniers and towards the climate actors.

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