Good People Making Bad Decisions: A ‘Community Solar’ Case Study

A solar power and battery storage decision

I nearly choked on my kale smoothie reading this article in the latest Renew magazine…

The Alternative Technology Association (ATA to its friends) is a wonderful organisation. They started as the Alternative Technology Cooperative in 1980 and ever since they have been urging Australians to think differently and more sustainably about how they use and generate energy.

In their very first publication, “Soft Technology” (created with the power of a typewriter and textas) you could learn how to make your own hydrogen at home.

Alternative Technology In Australia

homemade hydrogen

Don’t try this at home kids. Actually – do try this at home kids. You might learn something other than how to get to level 1,542 on Jetpack Joyride.

Name Games

A few months ago the ATA rebranded to ‘Renew’.

ATA to renew rebrand

Wot, no sun?

I don’t know why they did this, but I’m guessing that they decided renewable energy isn’t so ‘alternative’ any more. Personally I think it’s a mistake. I hate the new name. Bland, corporate, unoriginal. So I will be a curmudgeonly old git and keep calling them ‘the ATA’.

But I digress.

The ATA’s quarterly, now eponymous, magazine ‘Renew’ is put together by some of Australia’s most knowledgeable energy experts and I’m an avid reader.

Renew magazine

Despite me gently ripping one of their articles to shreds in this post, I highly recommend buying a subscription – a bargain at $34 per year1 – and full of ideas on how to live more sustainably in Australia. 

But this post is about how, not long after the latest issue landed in my reclaimed-wood-and-salvaged-steel-letterbox, I almost choked on my kombucha. I was reading a four-page article authored by a homeowner from Toronto, NSW and I couldn’t believe what I was reading. 

Blasphemy In The Energy Efficiency Bible

The article titled ‘A solar and battery decision’ talks us through a recently retired gentleman’s decision to spend $8500 on a 5kW solar system and $13,000 on a 7.5kWh battery. I’ll call this gentleman Fred2. Fred is obviously a top bloke because he chooses to pay more for grid electricity guaranteed to come from renewables using GreenPower. Not a lot of people choose to pay more for their electricity just because it’s the right thing to do3 so I started the article full of optimism.

However as I got further through Fred’s four-page feature, I felt both sad and angry. Not with Fred, but with the people and organisations misleading the Australian public about solar batteries. I couldn’t believe I had just read a case study of how to avoid cost-effectively making your home much more energy efficient, and how not to buy a battery.

The article embodies most of the mistakes well-meaning people make when they decide they really want a battery (thanks to all the misinformation and hype out there), then decide to twist themselves in knots making the economics ‘work’, often postponing or even abandoning more effective environmental, economical and comfort upgrades. All because they’ve dropped so much cash on a battery that will only lose money and hurt the environment.

This is a case study of the dangers of Australia’s current solar battery obsession caused by the media and well-meaning organisations breathlessly promoting grid-connected batteries as a silver bullet to the energy crisis.

Here’s a list of decisions described in the article that I consider misguided:

  • $13,000 was spent on a battery for a horribly thermally inefficient house. 
  • The battery was purchased as part of a bulk buy ‘deal’ by a ‘community solar’ scheme. Hence Fred got a battery that was too expensive, incorrectly installed, did not perform as promised and will almost certainly never pay for itself.
  • The battery purchase has depleted Fred’s working capital by $13,000 so the walls and floor – reportedly desperately in need of insulation – won’t be insulated any time soon.
  • When calculating battery payback the forgone feed-in tariff was overlooked (the #1 most common battery payback error)
  • The payback of the battery was blended with the existing solar power system to make the battery economics look reasonable (the #2 most common battery payback error).
  • Despite spending $13k on a solar battery, it can’t backup his home or even operate without the grid. That’s just lame.
  • The 5kW solar power system struggles to recharge the battery through winter.
  • The battery’s usable capacity is 25% lower than promised.
  • The battery’s power output is over 50% lower than promised.
  • $550 was spent on hardware for Reposit Grid Credits that looks like only earned about $11 in 18 months.

But it’s not all doom and gloom. Here are decisions documented in the article that I agree with:

  • When his resistive HW heater failed – he invested in a Sanden Heatpump.
  • He didn’t wait for the battery before he got solar panels.
  • His solar installation was a panel-level-optimised system that reduces the effect of his afternoon shade problem. 
  • He chose a high quality Winaico/Enphase solar power system.

It seems to me that an intelligent and well-meaning person has simply had their good judgement distorted by the battery mania in the mainstream and green media combined with good old peer pressure from the ‘community solar’ scheme. 

Let’s go through Fred’s 4 biggest investments to see what he could have done differently to both help the environment, his wallet and his comfort.

First Investment: Horribly Thermally Inefficient Home

The story starts when Fred bought a home that appears horribly thermally inefficient. That’s the first mistake right there.  At time of writing there are 67 homes for sale in Toronto, NSW. Surely some are thermally efficient?

When looking for a home, unless you have the capital to upgrade the thermal envelope, I would urge you to buy one that is reasonably efficient thermally. A nice home is comfortable and cheap to run, not an uncomfortable money pit.  

It never ceases to amaze me how one of the richest countries in the world shivers through winter in freezing houses.

Second Investment: Air-Conditioning

First thing Fred did after moving in was to buy a reverse cycle air conditioner, giving immediate relief from the heat of summer and the mild winters[ 1. I used to live in Dudley, just down the road – the winters were mild] . I can understand Fred wanting to be comfortable as soon as possible, and buying an air conditioner will immediately bring some relief in a badly insulated house.

The article tells us that Fred’s new air-conditioner can use 30-40kWh per day in winter/summer for heating/cooling. Wow. That’s not a house, it’s a tent!

Third Investment: 5kW Solar Power System

Fred has plans to renovate the main house’s roof space – so he put the solar panels on his shed: 260W Winaico panels. I love Winaico but would have looked at higher wattage panels. Then he could have oversized the panels to get 6.6kW of solar power with the same micro inverters for almost no extra cash. Whoever designed his system did him a disservice there.

But apart from the lack of oversizing, buying solar was a a good move. It is immediately cash flow positive, good for the environment and easy to do.

Also, buying an optimised system was smart – as his roof suffered late afternoon shading.

Fourth Investment – $13,000 7.5kWh battery

This is the bit that really started to sadden me. It was also the main thrust of the article. He wrote about the battery as if it was the most important upgrade of all.

Fred wanted to:

‘further decrease our use of grid electricity’


‘reduce our household’s evening peak demand to reduce the overall need for network upgrades’

In this post I won’t explore why I think this logic is wrong – that could be a whole post on its own. Suffice to say that this demonising of electrons flowing through the grid bewilders me. A strong grid that can happily handle large flows of electricity in both directions is critical in enabling a grid with a high penetration of renewables. Please can we stop demonising the grid?

If I was advising Fred, I would have given him 7 specific pieces of advice (whether he wanted my advice or not, I’m annoying like that):

1. Be wary buying solar or batteries from ‘community solar’ schemes.

Fred bought his battery from a ‘community solar’ scheme. Whilst I am sure the enterprise was well-meaning, I think Fred would have got a better system, at a better price, better installed that would give him lower bills and blackout protection if he had bought his battery independently.

Anyone who understands how to sell understands the power of seminars to persuade people to buy. I imagine Fred went to a seminar, and that increased his desire to buy, and that there was a deadline to be part of the ‘special deal’. I’m guessing this urgency didn’t give him enough time to do his research.

2. Shop around for the best battery.

I have never seen a community solar deal that is better value than simply shopping around. Fred paid $13,000 for a system with 7.5kWh of storage. That’s almost $2000 per usable kWh. That’s a terrible price. Back in 2017 he could have got a Tesla Powerwall 2 fully installed for that price (or even cheaper) and got 13.5kWh of storage, 5kW of power and ‘apocalypse proof’ backup. A Tesla Powerwall 2 would have been a much better system than a SolaX controlled LG Chem in my not-so-humble opinion.

3. Never accept a battery quote that does not do full backup.

If you are going to spend big dollars on a battery, you might  as well get backup included. It doesn’t have to cost more if you buy the right product. Ask specifically for a system that can ‘charge the batteries from the solar panels with the grid down’.

4. Don’t buy Reposit for the Grid Credits

I don’t know what persuaded Fred to pay $550 extra for Reposit – but I suspect a lot of it had to do with the promise of ‘Grid Credits’.

Reposit is a box that monitors your battery and allows you to – very, very occasionally – earn $1 per kWh from the grid when exporting. I have repeatedly asked Reposit to tell me how much money their customers have made from Grid Credits – but they refuse to tell me. At one point they claimed their system halved battery payback times (Ronald called BS). Anyway, I suspect that good old community peer pressure played a big part in Fred’s decision to buy Reposit too.

How much has he earned in 18 months from the Grid Credits? He reports he has had just 2 Grid Credits events in 18 months. The event he shares in the article earned him $5.36. So perhaps he’s earned about $11 in 18 months. Maybe that’s why Reposit refuse to reveal their customers’ typical earnings?

For $550 Fred could have invested in Solar Analytics instead. Which I consider essential for any solar system owner4.

5. Know your rights under Australian Consumer Law.

Fred’s system clearly does not perform as promised. He thought he was getting a 10 kWh battery but his usable capacity is only 7.5kWh. He thought he was getting a 5 kW discharge/charging rate. He is only getting 2.4 kW. If the higher specs were promised (or implied) by the community solar scheme’s marketing – then Fred has a right to a remedy under ACL. I suspect that he doesn’t want to rock the boat and upset the ‘community’ by exerting his rights. I think he should! He tells us that he is using more grid electricity than he needs to because the battery can’t discharge fast enough. Also it will be less likely to charge fully on cloudy days if it can’t charge at 5kW.

6. Don’t mount a Solax SK-TL5000 outside. 

You are not allowed to. It voids the warranty and it could be dangerous. And I’m sorry, but under your awning is still outside.

Solax solar inverter and LG Chem battery installation

The installation published in Renew. That inverter has an ingress protection rating of IP20., meaning zero protection against water ingress. It must be installed indoors.

Solax hybrid inverter specifications

7. Calculate battery payback properly

It is clear from the article that Fred has not realised that you have to subtract the feed-in tariff from the usage rate to work out the per-kWh benefit of a solar battery.

To compound the exaggerated battery returns, he’s blended the negative battery payback with the phenomenal solar payback. The result: a misleading picture of the battery economics.

Fred’s Priority Should Have Been Thermal Efficiency

A good home is a comfortable home. A comfortable home is a thermally efficient home. A home that retains both the heat and the cool is a joy to live in, cheap to live in and good for the environment.

I would urge Fred to invest in fixing his gaps, glazing and insulation as soon as possible so that he is not blowing conditioned air into a house full of holes and heatsinks.

Unfortunately for Fred that investment might be some time away as he

“will have to wait a few years to rebuild sufficient capital”.

May I humbly suggest that it could have been a lot sooner if your well-meaning community solar scheme had not persuaded you to spend $13,000 on a battery that does not perform as promised, is wrongly installed, will not provide backup, will take 30 years to pay for itself and has no chance of lasting that long.

I’m often accused of being anti-battery. I’m not. I’m pro-truth. When battery mistruths peddled by well meaning but naive people and organisations gain traction, the result is often people living in homes with almost no insulation because their capital has been siphoned by a battery vendor with the promise of ‘battery savings’ and environmental benefits that do not exist.

By all means buy a battery if you want one and can afford a negative return. But first make sure your house is thermally efficient. Yes – I know gaps, glazing and insulation are boring and not sold by Elon Musk, but they are the foundations of a happy, healthy, sustainable and comfortable home.

Unfortunately the myth that batteries are the silver bullet to home sustainability is making efficient homes rarer than ever. Poor thermal performance of Australian homes is a tragedy that is literally killing thousands of people every winter. We need to get past ‘pink batts’ and make ‘gaps, glazing and insulation’ sexier than even the shiniest home battery system.


  1. Whatever you do, don’t tell them that if they gave all their content away online for free they could have a great business selling sales referrals to solar companies
  2. Not his real name
  3. The SolarQuotes® office in Adelaide CBD is 100% Greenpower because we can’t put solar panels on it
  4. although their battery monitoring is rubbish
About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of My last "real job" was working for the CSIRO in their renewable energy division.


  1. We need a supplementary website: Double glazing 3 quotes

    • I started one once but got bored very quickly. Windows bore the hell out of me. Someone should do it though!

    • Erik Christiansen says

      Too late. I’ve just ordered my windows from the truss manufacturer. If his windows don’t fit his prefabricated wallframes, then I know who to have a go at. The price wasn’t too scary, as I didn’t make all the windows double glazed – just enough for the 6 stars. (Single glazed in garage and the two workshops.) Admittedly, 100% biomass heating fuelled from the on-site forest eliminates black balloons, as does 100% solar powered aircon, so stinting a bit may well work in this particular situation. We’ll see.

      Trying to compare various window suppliers did my head in.

    • Info on windows exist by supplier. Do an internet search for Renew Windows Buyers Guide. Also there’s the WERS database:

    • To be clear, that article was written and contributed by a householder – it’s not written by Renew organisation. Many of your points are correct, and we should have included a comment by Renew following the article to that effect, as we often do in Renew magazine. “Fred” is an early adopter and enthusiast, and his priorities are clearly different to most people. Reading the article in the context of the whole magazine gives a more balanced perspective.

      At Renew we’re on the same side as SolarQuotes in warning against battery hype. We’ve consistently advised that solar batteries are not yet economic for bill savings alone, for example this paper from 2015:

  2. Whilst I understand there are no economic benefits of getting a battery system for a domestic rooftop solar system, the environmental benefits are still far more beneficial than simply buying green energy from the grid. All of the arguments so far against battery installations are based on there actually being green energy available from the grid when the home solar PV system is not generating power and they fail address the impact batteries have on offsetting peak demand. I am a Qld resident so I would like to focus on the energy generation situation in QLD. In QLD there is currently 716 MW of large scale renewable (Source: NEM), 2000 MW of rooftop solar and 12 MW (Source NEM) of wind connected to the grid. Considering there is only about 570 MW of pumped hydro storage in QLD, when the sun is not shining there is no available “Green Energy” and the sun doesn’t shine at peak demand which occurs in the early evening. Noting that demand in QLD varies from around 5000 MW to 8000 MW at peak demand. Therefore storing your own energy and using it, particularly when peak demand occurs is the only way to make an immediate contribution to shutting down coal and gas fired power stations. I realise that the extra money spent on “Green Power” goes towards investment in Renewables when there is insufficient “Green Power” in the grid to go around, but there is already a significant amount of solar and wind projects that are struggling to get connected to the grid because of the grid’s inability to deal with more intermittent large scale renewable generation and relying on Government to fix the issue will get us no-where considering our State and Federal Government’s maternal attachment to the Mineral Council and their need for fossil fuel extraction.

  3. Ross Chapman says

    Hello Finn, interesting comments on the solar-battery hype.

    In your comments you have spoken about the over-blown “Grid Credits” selling point of Reposit (for NSW I very much agree), and you claim Solar Analytics is a better system for any solar system, although you also state that the battery monitoring software in Solar Analytics is rubbish.

    So, my question is: Would you recommend Solar Analytics or Reposit for a 3-phase grid feed house with a 8kW of panels, a 5kWh Solax hybrid inverter (like Fred’s) plus battery charger and 13.5kWh LG Chem Resu batteries??

    • Personally, I’d buy a Powerwall! The Tesla App is very good. I have Tesla + Solar Analytics and it is everything I need.

      The Reposit App has everything you’d ever want in terms of battery monitoring – last time I checked the solar monitoring wasn’t as good as SA though.

      I’d say knowing your solar is working 100% is a priority – so SA with the SolaX app to monitor the battery (assuming the SolaX app isn’t awful).


      • Ross Chapman says

        Hmmm… I think you still pay a premium for the Tesla name; LG Chem batteries are just as good – and I already have them!
        I am hoping to get either Reposit (currently one Reposit meter installed before we changed to 3 phase power, but disconnected from the web as it was giving some strange readings) or SA, both with enough CT units to measure all 3 phases.
        Solax does measure battery criteria, but I don’t have a mobile phone app and I don’t think it has active solar/battery management like Reposit.


  4. Hey Finn,

    Great article and I support your position 100%.

    I used to read and enjoy Renew magazine many years ago but I stopped a few years back when I felt that it was coasting on fumes of optimism. Plus it sells some very weird trinkets.

  5. Laurens Bloem says

    From that photo I’m guessing Fred’s real name is Hugh?

  6. R Barton says

    Good article Finn. II had experiences with several solar systems to my house in the Sth Highlands (that has inclement weather) – the 1st was a response to the initial 10 yrs ago which fed the grid. it did it job but efficiency waned, the 2nd was by a competent firm and is still operating effectively. The 3rd was with a community based organisation that had Reposit at a greater cost than you mentioned. The 1st battery failed and didn’t work and had to be replaced – it was hard hard to make contact with the mgt group and the installer cut his losses. I concur with the comment on Reposit. the 1st installation did not the features that they were referring me too. I subsequently found out that they had upgraded their program to operate on a mobile phone which has a lot more features. I concur that it is impossibles to work out the benefits – but my system has failed to operate on occasion and the Reposit monitoring has given the safety warning of these failures. A 4th installer ( a recommended by your standards) has upgraded and modified my system and it more effective and reliable. I agree with your views about some of the shonks and poor qty eqpt being sold. I found your book good to not being caught by some sales persons and installers

  7. Finn,
    I was one of the assessors for one of the early Solar buys. All we did was to assess the offers, & make a decision for the bulk buy. The Solar Co then did the ´Sale´. At the time the offer was reasonable…. Unfortunately still had salesmen involved.
    Re the Batteries, I totally agree. I am in 2 minds about installing one, & I would be doing it on the cheap! (Victron charger/inverter, & used flooded L/A battery.) I have 14Kw on the roof so no trouble keeping the battery charged.

    Re the FIT: It is worth reading the EV report, that has some interesting reading, such as the forecast the FIT might disappear, & batteries to become common.

    I am also a long term supporter of ATA/Renew. Of course, everyone publishing makes bad assumptions at times. I also used to be a Tester (1970´s) for Choice Magazine…. I rest my case!

    Re Reposit, I also looked at their system. I totally agree with your assessment.
    I wonder how the energy companies will buy power from consumers? It is quite possible to have an Open Source controller that will tell a battery to export (providing you can get the information to control the charger/inverter: not all are available!). All the Power reseller needs to do is to do a meter read before & after the export to audit the amount exported. A Reposit box is not necessarily needed & a bit expensive I feel.
    There is talk about a Communication standard for Inverters. I hope it happens soon & is adopted.

  8. Erik Christiansen says

    First, a safety warning on the electrolytic hydrogen generator. The stoichiometric mix of hydrogen and oxygen produced in it is highly explosive. Just over half a century ago, one of my shoolmates was absent for a day, then came to class heavily bandaged. He had had the foresight to crouch down behind the grasscatcher on the lawnmower when running just such a gas generator, using a jam jar with screw-on lid. Unfortunately, it slipped, the electrodes touched and arced, and high velocity glass shards sprayed the small garage. A U-tube, preferably soft plastic, would separate the gases.

    Secondly, the 7th bit of advice on the battery purchase. Not only is he $13k behind on much-needed insulation investment, the 30-40 kWh aircon consumption is perhaps up to twice his PV generation from a meagre 5 kW (peak) array, especially with shading issues. That means 20 kWh of grid consumption which could have been avoided if the battery cost had been better invested, as you describe. Add in concurrent household consumption, such as water heating, and grid consumption escalates further.

    It is remarkable that the ATA would feature such a badly designed system.
    (I don’t subscribe, but buy most issues of Renew, just skipping the occasional insubstantial one. There’s a lot of good reading in most of them.
    The honeycomb curtains may be a great thermal tweak for single glazed windows.)

  9. The round trip efficiency of battery storage systems (typically around 85% I believe) means that for every 10 units of energy excess energy that is stored only 8.5 units are usable. The argument is that by exporting these 10 units of energy you are directly reducing fossil fuel energy use by 10 units, whereas if you store it and then use it you are only reducing fossil fuel energy by 8.5 units. This would be true if there wasn’t excess renewable energy being fed into the grid that is not being used. There has been a huge increase in the amount of rooftop solar in QLD in the last couple of years and there is currently about 2000 MW of rooftop solar generation capacity which more than doubles the amount of large scale solar in QLD at around 713 MW.
    Wind is around 192 MW, Hydro is around 738 MW and pumped storage is around 500 MW. Coal fired generation is 8,186 MW and gas is around 3,490 MW. Based on NEM demand data for QLD from the month of May our electricity demand varies from 5500 MW during the day, 5000 MW in the early hours of the morning to around 8100 MW. Due to the amount of rooftop solar the minimum demand often occurs during the day and the peak demand often occurs in the early evening, when there is no solar generation.
    Considering that coal fire generators can only modulate down to 60% generation capacity the minimum amount of power they can generate is 4,991.6 MW. If roof top and large scale solar was generating at full capacity on a sunny QLD day in the middle of day when the demand is at 5500 MW and about 50% of rooftop solar generation was being exported the total solar generation would be about 1713 MW. If 520 MW of this being used by the pumped hydro system to store energy, then we would have 1213 MW being fed directly to the grid.
    Therefore, we would only need 4,287 MW from coal fired generation to meet the demand. However, they can only modulate down to 4,991.6 MW, so that’s a total of 704.6 MW of excess power being generated by coal fired generation because they cannot modulate below 60%. This does not even consider the wind energy being fed into the grid. Therefore, battery storage could store this excess energy and use it to reduce the peak which occurs at night. Although there are round trip losses in battery storage it is still storing excess unused renewable energy and using it to reduce fossil fuel generated energy.
    Please note that the above example doesn’t consider transmission loses however both coal fired generation, large scale solar and wind are likely to have transmission losses although the actual amount will vary due to geographical location.
    Am I wrong…..or missing something here…?

    • Hi Andy, the Qld grid is part of the NEM, so any extra solar generation can be sent through to other states on the NEM if it is more than is needed in Qld at that moment.

      • One might argue that we would export excess renewable energy generated in QLD to other states however most of the solar and wind in QLD is at least 2,000 km from the state borders and the transmission losses would be huge, besides that we have the same issue across the whole grid as we have in QLD. When looking at the entire grid we have the following generation capacity: Coal fired generation 21,006 MW, gas fired generation 11,294 MW, Large scale Solar 1,933 MW, Rooftop solar around 7,000 MW, Wind 5,220 MW, Hydro 8,021 MW, 185 MW of battery storage and 500 MW of Hydro storage. Total demand at around 1:00 pm in the afternoon is around 23,200 MW, this goes up to around 27,700 at around 5 pm which is around peak demand time of the day based on NEM demand data from yesterday which was a reasonably sunny day on the east coast.
        Considering that coal fired generation can only cycle down to 60% it would be contributing a minimum of 12,603.6 MW to the grid. If the sun is shining over most of the east coast and we are getting say 80% capacity out of the large scale solar system feeding into the grid it would contribute 1,546.4 MW. If approximately 50% of the roof top solar at 90% capacity across the east coast was feeding into the grid it would contribute 3,150 MW. Lets say there is a bit of wind on the east coast and the turbines are feeding 60% capacity into the grid at about 2,610 MW. Finally the hydro is going at about 80% capacity and feeding 6,416.8 MW. The total amount of generation would be 26,326.8 MW. The above assumptions, I feel are reasonable considering most the solar is in QLD and SA where it is sunny. This means that there is about 3,126.8 MW of excess energy going into the grid. Approximately 700 MW could be going into pumped hydro and large scale battery storage but that leaves 2,426.8 MW of excess renewable energy that could be stored by batteries coupled to rooftop solar. Even if there was just 10 MW of excess energy being generated by renewable sources that is not being stored by pumped hydro or large scale batteries that is still an enormous number of domestic scale battery storage systems necessary to store this energy to reduce the peak that is currently met with coal and gas generation. I’ve just discovered that RenewEconomy have. Website that tracks generation and demand from all the different generation sources and it backs up what I am saying above. I will record data over a full day and post it shortly…

  10. The problem to solar is being attached to the grid and since privatisation it will only keep going up.the entire goal is to go off grid,the tariff you receive does not pay for being on the grid,you are also correct there is so much misinformation out there,you couldn’t get me 3 quotes when i contacted your site,I had to contact others.efficient no

  11. I live in a thermally inefficient home (1970’s build with several unique features) and want to invest in energy efficiency improvements. But I don’t really know where to start.

    Are there domestic energy efficiency consultants who can do an assessment and assist work through the investment priorities for a specific home?

    I tried the Energy efficiency Council website but it’s focussed on corporate and industrial. It says residential as well but look for consultants and all you get are corporates.

    Our main need is draft proofing and insulation but I don’t know what to prioritise, there’s a lot of house, and a lot of (single pane) glass, and different ceiling set ups. Old fireplaces. Single pane skylights. etc

    • Energy Consultant says

      I own an energy efficiency consultancy and focus on business. We’ve looked at a potential residential market a number of times and we can’t see a viable maket there, in general, people don’t value the service. As Finn said, other than solar, it’s not “sexy”.

      To give you an idea about what we face, to paraphrase actual dealings with one of our clients, we recommend a number of measures for about $500k in investment with a payback from energy savings alone of just short of 9 months. You know what we got back? “What about rooftop solar?”

      • Thanks, I understand the difficulty with such things. It’s similar in my own field where expertise is undervalued. It’s a shame, I would certainly pay for an expert to make recommendations given a budget and to oversee the changes.

        As for your example though, what regular domestic home could possible make back $550k from energy efficiency measures in 9 months?! That’s more than most would ever spend on energy in a lifetime. Sounds more like a large residential apartment complex or enterprise than a single domestic dwelling.

        So where does one go for sound advice?

    • Ronald Brakels says

      I’m in Adelaide and I don’t know anyone who does a European style residential energy efficiency check where they measure drafts and use an infrared camera to check insulation effectiveness. While there must be someone capable of doing this it’s obviously very rarely done.

      • Thanks. At least I know it’s not my search skills that are lacking! Makes it hard to get sound independent advice on energy efficiency measures, what the options are and what sort of ROI I should expect from each so I can at least prioritise.

    • Erik Christiansen says

      Failing alternatives, a few hundred dollars spent on a NatHERS “6 stars” evaluation on your house would firstly tell you how bad it is, and secondly indicate the worst sources of loss, I figure. Just googling the minimal wall and roof insulation requirements for a new build gives immediate guidelines for your upgrade.

      Practicality suggests that plugging draughts is probably quickest, easiest, and cheapest. Hardware stores stock cans of polyurethane foam, and slats, rollers, and brushes for the bottoms of doors. Make sure that external doors close against narrow battens nailed inside the doorframe to stop draughts on the remaining three sides. The thickest batts which fit in your walls would be good, but ripping off the plaster or cladding is usually impractical unless it’s being replaced, and if it’s double brick, then forget it. Blown-in stuff may be the solution for a retrofit, though it’ll settle in time, and placing it both above and below noggings beats me.

      There’s an 8 page article “The key to thermal performance: Insulation buyer’s guide” in Renew issue 140. On p84 it says that 10% gaps in a wall of R2.5 batts will lose 64% of the insulation’s effectiveness, due to the thermal shortcircuit. That’s also the issue with an article on nifty honeycomb curtains. OK, there are companies offering various levels of conversion from single to double glazing, but fitting some double walled curtains with insulating airpockets is a less intrusive alternative or adjunct to what a cobbled-on additional (often polymer) glazing layer might offer.

      I go through over ten tonnes of firewood per cold season heating a lounge & dining area 11x7m, with cathedral ceiling peaking at 5m. Ceiling fans help to bring the warmth back down, but 11m of uninsulated external double brick wall plus large areas of single glazed aluminium framed windows defeat the insulation in the roof and remaining walls. Pelmeted curtains have made a big difference – by trapping an insulating air layer against the windows.

      If I had to pay for the firewood, I’d have double insulated the windows years ago, as I’ve done with the one a meter to my left as I type, to stop my left shoulder freezing from the cold air falling from its inner surface in winter. (That hack is just a large piece of double walled polycarbonate closely fitting the aperture in the brick wall, making the window triple glazed, in effect. It lets in ample light, and I don’t need that view.)

      • Thanks for the thoughts.

        Yes main living area (~70m²) *with* 2m² of single pane skylight, not sure ceiling height but I guess 4.2m. Also a secondary living area (40m²) is also cathedral ceiling with same ceiling height.

        There are two very large brick and stone fireplaces, one in each living area. The place is surrounded by single pane glass timber framed windows and eight (8) aluminium single pane sliding glass doors. The majority of the external walls are actually windows or sliding doors.

        Fortunately it has a 2m wide eave surrounding the entire house, with the front a much larger under cover area we have set up as an outdoor living space (size wise imagine a motel reception drive in space). The double front door could use some work to draft proof, again surrounded by a lot of timber framed custom shaped single pane glass.

        The other half hates pelmets for aesthetic reasons so that’s out. I’m always dealing with the balance between form and function.

        The rest of the home has regular ceiling height and these ceilings do have insulation but the walls (brick veneer) I have no idea, however I very much doubt there is any insulation in them. I don’t know the quality of the ceiling insulation. I know the interior walls between the cathedral ceiling living spaces and the rest of the home are not insulated (these are timber clad with 20+mm thick hardwood). There will be some gaps between boards of the cladding, mainly due to any board that may have warped a bit over the years.

        Concrete slab with timber overlay floors in living areas, carpet for the rest except tiled wet areas.

        We’ve replaced the clothes dryer with modern heat pump model (use clothes line preferentially) and the pool pump with a modern multi-speed model. Both are way more efficient than their predecessors (pool pump alone is saving ~1800kWh/year). Hot water is standard electric element model running on controlled load. Given our tariffs there’s no point moving that to run from solar PV.

        Of the fireplaces, one we never use (it’s ridiculously sized at 1.8m wide – what where they thinking when they built it?!), the other is large brick construction and while it works OK it churns through wood at a great rate of knots and is not particularly efficient. As such I mostly use it for ambience when we have visitors. Else heating and cooling is via reverse cycle air con units. The main living area, bedrooms and main bathroom are on one ducted unit with 3 zones, other living area has a unit as well. Individual reverse cycle units for living area and bedroom are simply not an option due to the house design. Kitchen is open to both living areas, zoning off areas isn’t really much of an option.

        I’m thinking:

        1. Draft proofing
        Can do the two regular hinged doors we have.
        The large double front door is problematic though as there is no door jam on the floor – it’s continuous floor from inside to out. At the moment just have a couple of floor snakes pushed against it.
        Not sure what if anything can be done to draft proof the sliding doors or timber frame windows (which are mostly hinged at the top and open with winders).

        2. What to do about the single pane glass everywhere?
        There is a LOT of glass in this house. It’s understandable given the views we have.
        I’ve read about film treatments and read a NZ study on them but I really can’t get a sense of whether such treatment is worth it. What options are there to retrofit to provide something akin to double glazing?

        3. Skylight replacement
        I can see us replacing the skylight with a more thermally efficient version and we desperately need to be able to have some form of shade control for the skylight. In summer it lets in a lot of heat.

        4. Heating and cooling / Fireplaces.
        This is a mild to hot climate (Northern NSW) and summertime cooling is the biggest energy draw by far. Dwarfs everything else. Being a little inland it does get pretty cool as well (single digits C but rarely would we see a frost).

        Completely remove the excessively sized fireplace and replace the other with something more effective for heating and then use the wood heater more often, and ducted unit less often. The trade off with the large fireplace removal is it’ll end up getting replaced with more glass (views again). At least we can specify something far more thermally efficient for that section of new wall.

        5. Get an insulation review and consider adding insulation to interior walls between cathedral ceiling living spaces and the rest of house ceiling cavity. I doubt insulation is possible to add to the exterior walls (brick veneer and noggins are you say). It might be the existing insulation is pretty crummy.

        6. Curtains / pelmets
        It’s just not the sort of place where we are going to have thick curtains everywhere and the other half hates pelmets. Aesthetics and visual design considerations matter a lot to the other half, and there will likely be a thermal efficiency price to pay as a result.

        7. As they come up, replace appliances with high efficiency models. Fridges are not all that old so likely not so bad. Have done pool and dryer. Washing machine will be next. Hot water unit I suspect will be some years away before it needs replacement. At the moment HW represents ~ 7-8% of total energy consumption, which is unusually low, mainly because total house consumption is very high (average is ~46kWh/day).

        8. Lighting is not a big energy draw in the grand scheme and for the most part we have energy efficient lights.

        9. Take advantage of opportunities during any renovations. We have some ideas for partial reno work and where walls etc are exposed, moved/rebuilt, well insulate and draft proof the crap out of ’em!

        I get the value of draft proofing and insulation. I have no sense of whether glass thermal film treatment is worthwhile investment, or if there are alternatives to consider for our all out glass.

        • Erik Christiansen says

          Given “This is a mild to hot climate (Northern NSW) and summertime cooling is the biggest energy draw by far.”, I’d aim for an R5 ceiling, using reflective backed batts, and provide ample summer window shading on the north and west. The 2m eaves should just about do that.

          A big PV array would power the aircon(s) on hot (sunny) days, so consumption is neither expensive nor climatically destructive. That’s a darn sight cheaper than doing all that glass in one hit. (I’d sneak up on that if winter is cold.)

          The 1.8m fireplace can readily be blocked off with a chimney flap, just up inside. Alternatively install a slow combustion woodheater in it. A fireplace is generally 10% efficient, while an enclosed heater is usually around 40%, so wood use should drop by 75%.

          Any downlights? They are often open straight through to the ceiling space, leaking warm air and drawing in cold air elsewhere. (Even one unsealed ceiling light would invalidate my 6 stars for the new build.)

          Door snakes or affixed weather strips are less of a trip hazard than a batten on the threshold.

          As for window films, they can be useful on the west and north, to reduce solar heat load if the windows are not shaded by those wide eaves in summer. Have a look at ; typing “windows” into their search bar, I found
 which will give you a primer on thermal conduction calculations and solar gain. Armed with a bit of background, it can be fun to wade into deeper internet waters.

          • Thanks.
            – R5 ceiling batts. I’ll talk with an insulation company about a general insulation quote and see what they say about walls.
            – Solar: I already have an 11kW solar PV system
            – Chimney flap, will look into that. Unlikely to install a heater inside it (certainly there is plenty of room to do so though!) as we would prefer to demolish it entirely.
            – Downlights, there are three I can think of, old style fittings so a fair chance they are draft points. There are also a number of old ceiling speakers not connected to anything anymore. The baffle covers I would imagine are not going to let much of a draft through but they could be sealed with something I guess.
            – Front door threshold, yes I think weather strips of some kind would be a better bet. Possibly also some draft proofing for the surrounding frame. Need to think about the gap between the doors.
            – I think also we can look at better draft seals for some internal doors for the laundry and bathrooms.
            – window film – the eaves do a good job dealing with direct sunlight for the high summer for the hotter part of the day, perhaps only late afternoon sun on the western windows (there is some natural shading). I’m just not sure if such film will improve the thermal efficiency as it’s conductive heat rather than directly transmitted. I’ve also been looking at retrofit double glazing although it’s pretty darn pricey.
            – I think the skylight windows need replacing with a higher grade insulated double or triple glazed windows with a controllable blind. The sun just thumps in through in summer, and heat must just be waltzing it’s way out in the winter.

            All good ideas. I’m guessing based on costs, the options based on increasing ROI are:
            – preventing drafts (doors, downlights, chimney and windows)
            – upgrading insulation
            – working out what to do with all the single pane windows.
            – when / if we do some renovation, then make sure we take advantage of that to ensure we substantially improve thermal efficiency.

          • Erik Christiansen says

            Alex, the ceiling R5 can be made up of batt + reflective foil + air gap + plaster. It’s the sum which counts.

            A self-adhesive foam strip between the double exterior doors will probably wear fairly quickly with frequent use. A dense self-adhesive brush strip would help, if you can find a short bristled one. A thin wooden cover strip, glued to the face on one side, would help. (I’ve done that to a bifold door, here.) Alternatively, a shiplap joint, made by rebating half the thickness of one door, and gluing a half door thickness solid wood tongue onto the other, would greatly reduce airflow and dust entry. To avoid the need for a close fit, a self-adhesive foam strip in the overlap allows a bigger gap, and cushions closure slightly.

            The second web link I cited is worth reading. It describes low emissivity and transmissivity coatings and their application. What’s best for a high western sun load in the afternoon, then becomes clearer. (Window manufacturers provide SHGC figures for their windows, so you’ll see immediately which have useful coatings.) A quick look at “double glazing” on wikipedia brushes up on terminology. Read up on “thermal break”. Explore. In short order, you’ll laugh at the thought of buying expertise – because it’s not that hard if you sneak up on it, and learn before spending.

    • Brad Sherman says

      Hello Alex,

      Not sure if my personal experience helps in your situation, but here goes. Shortly after moving to Canberra to take up a job at CSIRO (senior research scientist in environmental fluid dynamics), my wife and I purchased the best house we could afford at the time. It was late-60s/early 70s vintage which meant basically that it was brick veneer and roughly 30′ x 50′ rectangle. There was a bit of fibreglass fluff in the ceiling, but otherwise, no insulation.

      I’m originally from the USA and my wife is from Norway. Thermal performance of Australian housing is an oxymoron.

      I’m going back a ways in my recollection but I’m confident this took place in late autumn (probably May.

      First step was to install ducted heating. I deliberately did not insulate first because I wanted to quantify the impact of the insulation on gas consumption. Note that ambient weather conditions didn’t change that much during the experiment to have a consequential impact on the results.

      Step 2 was to fix the thermostat at 20 C and record the daily gas consumption.

      Step 3 was to install ceiling batts. In those days I had to argue to even get R4.5 – Contractor: “Mate, are you sure? It’ll cost. People usually just ask for R2”. Me: “It’s my money, dust quote for what I asked.”

      Result: Immediate 25% reduction in gas consumption.

      Step 4 was to blow insulation into the wall cavities.
      Result: Additional 25% reduction in gas consumption. So the net effect of the ceiling plus the wall insulation was to lower gas consumption to 0.75 * 0.75 = 0.56 of the pre-insulation value. A 44% reduction in gas consumption and an immeasurable increase in living comfort.

      My experience is: don’t wait to insulate the ceiling and the walls. My were just thin sheets of gyprock. I haven’t insulated the floor because it’s reasonably thick timber which I assumed was a secondary heat loss path compared to the single glazed steel-framed windows.

      About 10 years later we undertook a major renovation, expanding the floor area by 80-90% and the volume by more because we put in raked ceilings in new areas (I’m pretty tall and don’t like 8′ ceilings). The new construction used 250 mm thick Thermacell expanded polystyrene blocks (cores are backfilled with reinforced concrete) which have a minimum of 80 mm polystyrene (40 mm either side of the concrete core). External brick walls had an extruded polystyrene layer added to them – the idea was to get the sun off the high thermal mass of the bricks so that they wouldn’t radiate into the house as much heat during the hot summer months.

      We’ve got a lot of glass and high windows. Everything is double-glazed with 4-12-4 low-e coated glass (on the inside pane). We bought the windows from Schuster in Goulburn – he had imported from Germany the machines for fabricating western red cedar tile-turn German windows. (Unfortunately, they no longer manufacture these windows but they are beautiful to those of us who like timber windows). If you are bothered by street noise, the acoustic insulation of double glazing is an added benefit but beware that there is a tradeoff between thermal and acoustic insulation objectives – acoustic performance is better with a larger gap (up to a point) which decreases thermal performance. My first DGU from Schuster was ordered back in 1992 or 93 and I had to order the low-e DGU direct from Pilkington in Melbourne. Low-e 4-12-4 was a standard glazing product in cold northern hemisphere clients (my wife’s home town in north Norway actually required triple-glazing) I was disappointed to learn from Pilkington that they had met only resistance from residential window manufacturers in Australia – again, no one in the common building trades was interested in new, better, or different. But if you persevere you can get it done.

      With nearly double the floor space and 250% more volume to heat, we were very pleased to find that our energy consumption was the same as before the renovation (same thermostat program for the ducted heating, etc). Clearly, insulation is extremely beneficial. As a guide to the thermal performance of the house in winter, on our coldest days here (- 5C overnight low) the house will cool from 20 C at 2300h to 15 C (coldest ever, typically 16 C) by 0700h the next morning. The heating never turns on while sleeping which has been great for me because the combination of gas heating and Canberra’s dry air had previously caused me to wake up with really dry throat and sinuses previously – this seldom occurs now and is another very important hard-to-quantify-economically benefit of insulating well.

      • Erik Christiansen says

        Brad’s: “My experience is: don’t wait to insulate the ceiling and the walls. My were just thin sheets of gyprock. I haven’t insulated the floor because it’s reasonably thick timber which I assumed was a secondary heat loss path compared to the single glazed steel-framed windows.”

        Yep. Although hardwood isn’t a brilliant insulator at R0.12 per inch of thickness, glass is five times worse at R0.025/inch. (Sorry, wikipedia isn’t metric.) OK, if floorboards are 19 mm (3/4″) thick, that’s R0.09, well worth thick underlay and a thick carpet, if not underfloor batts. (The stiff ones.)

        BUT, 4mm window glass is R0.025/6.35 = R0.004, i.e. about the same as an open window as far as conduction goes. (23 times worse than a bare wood floor, per unit area.)

        Honeycomb curtains are then a quick fix for the worst overnight heat loss, short of retrofitting double glazing with a low-e coating to reduce IR transmission, I figure.

        • “4mm window glass is R0.025/6.35 = R0.004, i.e. about the same as an open window as far as conduction goes.”

          Jeepers. We have 86m² of single pane glass.

      • Hi Brad

        Thanks for relating your personal experience. Having lived in Canberra in one of my former lives, I have a fair insight into how cold the old 1970s homes can get!

        Ceiling insulation upgrade seems to be a relatively straight forward step for us to take. Walls not so much unless cladding is removed. I’ll ask them what if anything can be done with walls.

        Windows and glass are going to be a challenge. We really don’t need much in the way of acoustic insulation as we live in a rural setting. It’s actually nice to hear the birds. The local highway provides a little background noise, almost white noise and is not of concern. It is not a heavy traffic road, certainly not when we want quiet. So it will be thermal properties of the glass I’ll be interested in.

        I think there are going to be rooms where retrofit double glazing will be an option. All the windows are timber framed. The glass sliding doors however are another matter as they are aluminium. It may be we bite the bullet with those and replace them. There are 8 of the buggers so it’s going to be pricey!

      • Denis Cartledge says

        “…no one in the common building trades was interested in new, better, or different…”

        Most aren’t interested. I suspect its because it wasn’t in their Apprentice years. However, some are but they aren’t prepared to do any thing about it.

        I Owner Built in a northern New England town and used Thermacell blocks throughout. I also used DG throughout. As I say to visitors all glass in the house is DG. Except the Oven and that’s triple glazed. 😉

        The Builder I used for stuff I couldn’t do, Slab and Roof, commented that this is the way we should build houses. Because in Summer after lock-up, the tradies would rock up and check my external temp reading then come inside into the up to 10C cooler room. I said to him we could work together, he builds, I consult on the materials.

        I have never heard from him.

        I also put in my own rainwater tank and everything water-wise is drawn from that.

        There is a lighter upside to how I built with its stable temperature (and humidity) and rain water.

        A friend decided to start brewing his own beer. And advice from others around town commented that if only they had good water and a stable temperature range it would be easier. He headed around to my house as, aside from the few air conditioned places around town, my place fitted the bill. The tankwater was also a strong incentive.

  12. Philip Venton says

    Further to your excellent article, it would be useful to discuss the enormous confusion existing in the glazing business. We completed a well insulated house last year, equipped with thermally broken aluminium frames and double glazed with argon fill. The overall U quoted was 3.2-3.6 depending on the window. In our first winter the windows appear to be performing worse than expected.
    The framing supplier advised that it’s not their problem, just that the glass should have been specified with a low e coating, and with plastic spacers which would have provided an overall U of around 2.1.
    All this after seeking advice at design stage from the window industry association, the window supplier and an independent heat load simulation to NatHERS and the consultants specification recommendation.
    Viridian’s “Lightbridge” glass seems to be the product of choice.. located at the end of their 130 odd page technical brochure. The glass coding in the WERS Certified Products Directory is almost unintelligible.
    We would have been comfortable spending more than the $85,000 on the doors & windows to achieve god thermal performance – but were not offered (or even discussed) the option.
    PS – Tesla repaired our electrical storm damaged Powerwall and it, and a second battery are performing well – not an economic decision, but the solar power generated for home heating stays on our side of the meter – so feels good!

  13. ….groan…. I DO wish people would refrain from chanting this demonstrably false mantra (“Whilst I understand there are no economic benefits of getting a battery system for a domestic rooftop solar system,”) without checking their “understanding” against the FACTS. One such fact is that the mantra MAY be near-accurate if one simply (simple-mindedly?) adopts the ‘accepted’ industry standards and refuses to consider the alternatives. You know:- Take the same approach that moved you into alternative energy in the first place in the face of all the negative ‘understanding’.

  14. These people discourage using solar/ batteries because the power companies pay people to discourage you against solar so they keep getting massive profits by ripping us off.

    • Alex Simmons says

      If the power companies are deliberately dissuading people then they’re doing a pretty crap job given over 2 million Australian homes have solar PV systems and the growth rate of new domestic solar PV installations is not slowing down.

  15. Pretty sure this site isn’t discouraging solar.

    The clue’s in the title.

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