This is part 2 of a 3-part series on household emissions in NZ. Part 1 looked at whole-of-life emissions from housing, and this part does the same for transport. Part 3 will tie them together.

Last time, I started with a graph showing the carbon footprint for an average New Zealand household, with transport very much in “big toe” position:

Stats NZ have kindly provided more of a breakdown on the transport figures, letting me make the new graph below:

An average NZ household creates 5.2 tonnes of ‘direct’ emissions a year from using petrol and diesel, with another 0.9 tonnes of ‘indirect’ emissions coming from the supply chain. These figures will vary between different households. ‘Household composition’ makes a big difference – is there one adult who drives to work or are there four flatmates who all drive? And there are regional differences: Wellington households have consistently lower emissions than Auckland ones.

But today I’ll focus on the difference that location makes within the Auckland region.

So how can we measure transport emissions for households in different locations? There are several different data sources we can use, because there’s a largely linear relationship between travel, fuel consumption (or fuel spending), and emissions. On average, cars use a litre of petrol for every 10 km they travel (real-world results, often 30% higher than the lab-tested results that get quoted), and that petrol will create exactly 2.3 kg of emissions.

There have been a number of New Zealand studies using these various data sources, and we’ve often featured them on Greater Auckland. These include Peter Nunns’ analysis of census commuting data

… and my analysis of petrol station spending data. With a few assumptions, I can convert this into an estimate of emissions (including the upstream ones):

There isn’t a straight-line relationship between distance and emissions – it’s logarithmic instead, which means that the biggest increases come early on (e.g. emissions increase more going from 5 km to 10 km than going from 25 km to 30 km). But they do increase throughout. People living a long distance away from the middle of town travel much further distances – not just for work, but to access education, shops, services and so on.

The equation on this graph suggests that a household living 5 km from the city centre will create five tonnes of driving emissions a year, a household living 10 km away creates six tonnes, and a household living 30 km away creates seven tonnes.* 5 km would be Balmoral, 10 km would be Stonefields, and 30 km would be Kumeu, Takanini or most of the other places where Auckland is sprawling.

Looking ahead to the next decade when major decarbonization will be required, it will be much easier for central households to cut their emissions than for remote households.

Even just looking at the existing emissions, the difference between five and seven tonnes might not seem huge, but it is significant. If anything, I think it’s understated for new housing. A lot of the outliers below the trend line are town centres – Papakura, Warkworth etc – and I suspect that people have historically chosen to live there because they work nearby. New subdivisions are more likely to be above the trend line, as these new areas tend to take on a much larger share of housing growth than they do of employment growth. Unless transit is built in from the start, they’ll probably be more car-dependent than the suburbs next to them.

Lastly, a quick reflection. “Food and beverages” slots in between transport and housing in the average carbon footprint. I was honestly quite surprised at how big a contribution it makes. I mean, I love meat, and I don’t drive much, so for me it’s probably the big toe (or a delicious Achilles heel?). My third-ever post for Greater Auckland said that “as consumers, the best thing we can do to reduce our contribution to global warming is to change our transport habits”. But our eating habits are right up there too; I’ll certainly be taking another look at mine.

* I’ve done some regressions against demographic variables – household income, household composition and the average number of people employed per household – which still give very similar results for the distance effect. 

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  1. Distance clearly matters but so does the level of deprivation of neighbourhood. The work of Caroline Shaw at Otago School of Medicine indicates that in relation to land based transport emissions, those in the least deprived areas have emissions nearly double that of those in the most deprived areas. Her measure does not include aviation. The Statistics NZ household measure does include domestic flying but does not include international aviation. If you look at the data for 2018 estimates suggest 80% of aviation emissions come from international aviation and 20% from domestic. Again overseas data suggest a very strong income effect, with much higher aviation emissions from the better off. We tend to avoid ‘class’ based analysis in New Zealand, but in terms of figuring out ways of reducing household and individual emissions we need to delve in deeper as to who has the largest footprints.

    1. Yeah it makes a huge difference. And that flights footprint “per household” is one of those measures where the average doesn’t tell much of a story compared to looking at how many households are way over it.

      Interesting, though, in the same way that “gentrification” wouldn’t happen if all suburbs had good, safe, walkable, bikeable infrastructure – the evidence is now that car ownership in the UK has dropped at least 20% over the last decade in places where people are relatively affluent and have an average age of 32. Young people, if they can afford it, are flocking to places where they don’t need to have a car and can cycle instead.

      Also low traffic neighbourhoods have been shown to lower car ownership rates by 20%.

      We need to make sure our population get rid of their aspirations for frequent flying, and we need to make sustainable transport lifestyles available to everyone.

    2. Did the study include the “lifestyle” block belt? Or carbon emissions from boats, jetskis, ride on mowers, Harley Davidsons etc etc. I’m sorry, but the study really isn’t that insightful when it excludes so much.

      1. It’s still insightful if it helps with a piece of the puzzle. I was looking in depth at another study yesterday which was based on odometer readings for all cars at each household – too old unfortunately to bother blogging about, although if someone updates it, the changes will be very interesting to see. It definitely showed relatively lower household transport emissions for people along the train lines.

        The wealthy areas were definitely higher in transport emissions for their level of proximity than they should be. Driving long distances for holidays or weekends away is probably a big factor. Since the wealthy seem to go on holiday with nearly one car per driver these days, this will be even worse now.

        1. Those train lines that are either closed or 40km/h max? After 4 weeks of no service, the southern line is back again, still 90 minutes + Pukekohe-Newmarket. Half an hour wait at Pakakura!!

    3. I haven’t come across Caroline’s work before – do you have a link Paul?

      I didn’t include deprivation index score in my regressions, but did include median household income and average household size, there would be a reasonable correlation between those variables and deprivation.

      The ‘carbon footprint’ figures in my post do include international aviation by NZ households, although I’m a little curious of Stats NZ’s results on this as the figures look higher than I’d expect, and Mōtū got lower results when they looked at it a few years ago.

      But yes a very strong income effect and int’l travel can be a huge factor in our emissions, as per this post

      1. After attending a talk by Caroline I communicated directly with her and she sent me the graph (her e-mail is on the School of Medicine website). Probably best to do that as I dont think the study has been published yet. Good to see that Stats data does include aviation. It was hard to pick up looking at their technical notes.

    4. The flight footprint for our population even just for domestic travel is eye opening.
      Related to food production, I would like to see farmers given credit for soil sequestration and so far that doesn’t seem to be done. Also it would be nice to see credit given for trees other than plantation forests. These trees act as shelter and soil stability in steep country where Prof x on the junction of New Plymouth / National Park Junction advocated 60% canopy for hill country farming in the Papa country.
      This type of farming probably has a positive rather than a negative carbon footprint which should count in the production of the meat/wool etc. Further more the willow/poplar is good drought tucker when judiciously felled.

      1. The co2 emissions around farming in NZ aren’t accurate at all imo. On paper its a terrible industry but through the use of GWP100 and very difficult conditions to measure stuff in, I think its an unfair representation that has come about through various political and education related reasons.

    1. You’re forgetting that engines suck in a lot of air. That 2.3kg of CO2 is made up of Carbon from the hydrocarbons that are petrol or diesel and Oxygen from the air.

    2. My bad, just didn’t look right at first glance, but as others have pointed out, it’s the combining of air with carbon that makes it larger than just the fuel content.

      1. The real problem is when the dephlogisticated air mixes with the miasma in town. It causes recurrent imbalance of the humours that can only be cured with an extended stay in the countryside and plenty of coca wine tonic.

  2. So we can affectively get rid of the petrol/diesel and supply chain categories just by moving to electric cars (assuming we have/build enough renewable energy).
    The food category is interesting. That is the amount we consume; I imagine we create much more then export it to others to consume. How is this typically measured by country; the country that creates the product or the country that consumes it?

    1. The emissions are counted towards the country of production. So a lot of NZ’s agricultural emissions are actually to support food consumption in other countries. That’s good on a worldwide scale though, as NZ can produce food with a lower carbon footprint than many of those countries could domestically (even once transport is factored in).

      It works the other way too. A significant industrial emitter is the cement production industry. NZ has domestic cement production that contributes to our emissions (Golden Bay Cement, part of Fletchers) and also imports cement from Japan that contributes to their emissions (Holcim).

        1. Most of our fuel is imported as crude oil, then refined by Refining NZ at Marsden Point. The refining process itself is a high emitter because some fuel is burned to provide process heat. Then there’s the domestic distribution supply chain, which is mostly coastal shipping followed by road tankers.

        2. So if we import it refined then we aren’t emitting anything (we are moving that way right?). Even the supply chain wouldn’t be emitting much would it; I imagine the majority of that is trucks using imported fuel?
          They really should measure consumption, production is stupid. I get the feeling they use whatever figure proves their point at the time.

        3. The usual approach for measuring emissions is production-based, rather than consumption-based like the ‘carbon footprint’ stuff in this post.

          Using a production-based approach, the fuel is imported, but (most of) the emissions are produced in NZ as that’s where the fuel gets burnt.

          As LogarithmicBear says below, emissions from the refining process in NZ would also be counted, whereas emissions from getting the oil out of the ground overseas aren’t counted.

        4. Yes the trend is towards importing all our fuels refined. Transport from South East Asian refineries to the petrol pump still counts as a supply chain emission though.

          The thing with emissions from domestic production of things is that its something our regulatory settings can change. For imported goods we have little influence over production methods because we’re such a small part of the market.

    2. The carbon accounting area is a very difficult problem to solve, often it involves huge amounts of international politics deciding on which country takes ownership for which c02 emissions and how much each different gas counts. Part of which is using a c02 equivalent scale for everything, short and long lived gasses alike. Through GWP 100. I think the govt kind of dropped the ball on this one, signing on to accept this measuring stick as a part of one of the accords (kyoto or paris I cant remember). Using an average warming over a 100 year period means that methane is counted much higher than c02, because c02 has a much longer life in the atmosphere (100s of years vs ~12 for methane). It effectively subsidises c02 emissions and makes methane emissions pay for it.

      1. Are you suggesting they don’t take into account the fact that methane is short-lived when assessing its relative impact? That seems extraordinary.

        1. I’m suggesting that they over represent methane. They do take into account that it is short lived, but they don’t do enough. GWP 100 takes the sum of the heating caused by the gas over a 100 year period and uses that to compare gasses to co2 coming up with an conversion chart. co2 is there forever essentially, and methane is gone after 12 years. 100 years was considered a happy medium by co2 heavy countries, whereas NZ gets totally shafted by that. The second link is more relevant.


        2. To add to my above comment:
          I am running under the presumption that Stats NZ is publishing statistics based on the GWP100 equivalence. And rightly so, this is the number that everyone (including GA) publishes. I am not able to confirm this however despite trawling through the MFE website for an hour. I have emailed them, I’ll see if they get back to me.
          I’m saying that the stats are “wrong” at the moment, and the MFE paper agrees. I cant blame them though, this is what the Kyoto protocol said to do, and politicians agreed for various reasons I’m sure, but its bad science. Measuring global warming potential as a single number, co2e, doesn’t make for accurate statistics. Although it does make it easy to understand.

  3. No more cycleways manufactured from concrete. 1 kg of cement leads to 1 kg of CO2.
    Bitumen is a better material. Except its black so it absorbs heat while concrete is white so it reflects it. Hard to know really there are companies trying to make so called green concrete but its a bit hard to turnaround an industry which has an average plant production size of 700,000 tonnes per annum. There’s some pretty quirky ideas including sequestration of CO2 in concrete but could the ideas match the scale. Overall the cement industry leads to 7 percent of the worlds emissions about 3 billion tonnes per annum.
    On the subject of material for cycle ways it has being suggested a compacted clay, sand fine gravel mix with some kind of water repelling polymer could be used but it wouldn’t have the low rolling resistance that concrete has.

    1. In the South Island asphalt footpaths are much more common than concrete. In the upper North Island concrete footpaths are the norm. I can come up with various theories why this might be the case but would love to know for sure.

      Bitumen is a crude oil derivative, so it comes with non-trivial supply chain emissions attached. When the transport fleet is eventually electrified and demand for oil dries up then bitumen will probably cease to be available. It isn’t a high value product so won’t be able to support the supply chain on its own. An example of this is Refining NZ ceasing bitumen production from next year, there just isn’t enough money in it.

      There’s a lot of research (including in NZ) going into including waste plastic in asphalt. This can already be done to a limited extent. In the future it’s likely that waste plastic will replace bitumen as the binding agent altogether.

        1. Yes and building roads with plastic in them won’t help in this regard, though it’ll probably have less of an impact than the contaminants from the vehicles on the road (tyre rubber, brake dust etc.). The use of waste plastic will mean intercepting a waste stream that would have ended up in the environment anyway and repurposing it.

          Ideally the transition to a circular economy will take care of the problem that is waste plastic. But there doesn’t seem to be enough political will pushing in that direction yet.

        2. Absolutely. We bought insulation made from waste plastic for exactly this reason. Also, they were prepared to take back the scraps and put back into the system.

          And I tried to encourage the local community centre to buy outdoor furniture from the firm in NZ that puts together the pieces from the Australian manufacturer who was taking our plastic bags. About that time, the Australian manufacturer said they couldn’t take NZ’s any more because they have to prioritise their suppliers who also buy their stuff. I didn’t follow how that eventually got resolved.

          We’re about two decades behind the ball on this. I do worry more when plastic is used as a landscaping material than when it’s a product which could, in theory, be contained and recycled.

  4. What will NZ Refining do with the heavy residue if it isn’t turned into bitumen. Can it be reacted with Hydrogen to make lighter hydrocarbons like diesel or jet fuel. What about the sulphur. If the hydrogen was produced with renewable electricity the fuels produced would be semi renewable. Also if oil goes extinct then there will have to be other ways of manufacturing the pre cursors for plastics. I would love a time machine so I could go ahead and see what actually happens.

    1. That is a good question, I haven’t seen a definitive answer to that. Maybe they plan to re-export it? There must be plenty of backloading capacity on tankers visiting NZ.

      1. They’ll load it into tankers alright – just not the ships cargo hold more like the fuel tanks!*

        Effectively removing the CO2 emissions from NZ’s “quota” when the ship sails outside the borders of NZ.

        *Yes I know the international maritime rules on sulphur content in bunker are supposed to be minimising this. But only when close to land. Out at sea – its out of sight, out of mind.

  5. The slow downward trend of CO2 emissions has been reversed. SUVs and large utes are much more danger to the environment than smaller cars.
    They are dominating sales and producing huge amounts of emissions. The inter energy agency, IEA found that they are the 2nd largest cause of the rise in CO2 emissions. (Report in The Guardian)

    1. Increasing the price of carbon credits (and by extension fuel) in NZ will help with this. Which I believe is the plan under the current govt

      1. Why not tax the vehicles directly relative to their carbon emissions? And stop taxing modern fuel efficient motor scooters off the road, they have the lowest carbon emissions (esp including manufacturing) of any ICE road vehicles.

        1. Vehicles are in effect, charged based on their emissions. The more liters of fuel you burn, the more you get charged in carbon credits. And like some other commenter said, carbon accounting means manufacturing emissions are counted against the manufacturing country. So presuming we follow through with trade tarriffs on stuff imported from those countries that fake, or dont care about c02 emissions then we’d be good there too. A lot of my friends have scooters, and I never hear them complaining about the cost of fuel. $5-10 a week, significantly cheaper day to day than the bus even. Encouraging scooters might be better achieved by lowering the acc levy in the rego, or the rego fees altogether. They cause next to no road wear.
          And same goes for motorcycles, my 200cc bike costs $400 a year in rego fees. Which is absolutely insane.

        2. By modern fuel efficient scooters I mean the 150 cc class which are optimised for low consumption/low emission often including features like idle stop. These are also hit with the $400 rego cost. I get the ACC cost but if you are serious about reducing carbon emissions, then that must take priority over accident costs. Especially since NZ typically has far fewer rego “steps” than most other countries. 125s are hit with the same cost as 650s which is ridiculous and fails to recognise the difference between basic a to b transport and weekend toys.

        3. +1 This is a class of vehicle which almost doesn’t exist in NZ because of the rego issues. It would be a fantastic change.

          And there could be changes that AT could make too, more parking for scooters at park and rides with a simple bar to chain your bike to. The way they set the parks up now at Albany for example isn’t very space efficient. Although it does stop people from dinging your bike, I would prefer a long box that you can fit as many bikes in as you can find space for. Most of these vehicles aren’t Harleys, and you don’t need to specifically cater to expensive bikes.
          Better bus prioritization helps motorcycles / scooters too. I want them to keep that forever. My other pet peeve is the southbound busway and busway onramp, from Esmonde road, is a bus only lane which is stupid. It should be a bus lane. Get split laning bikes out of the main traffic with no harm to busses.

        4. The reason your motorcycles and Mopeds costs what they do is due more to ACC levies which those registration prices include than anything else.

          Thats a different discussion for another day.

        5. I’m saying their carbon emissions profile should take priority over ACC when deciding rego costs. ACC is a local construct, not an unchangeable natural phenomenon. Discussion is all we have in NZ, in reality everything locally is set up to increase transport emissions. All hope is placed on electric cars which is really just coat tailing on other coutries while things here don’t change. We could do a lot more now but it would upset cosy vested interests.

        6. Then the clean car discount plan that the last government had, that the Handbrake of NZ First shit all over, would have reduced the up front costs of your moped or fuel efficient motorcylce on a carbon life emission basis.

          But probably not by very much. As under the original Clean car discount scheme each class of vehicle was managed separately from the others, so the moped and motorcyles would be carbon priced within their group of like vehicles only.

          Not by comparing the lifetime emissions of any moped to those of a car.

          While I’m sure some people would drive a moped instead of a car.

          The reality is that many would still have a car as well – using the motorcycle or moped for its cheaper running costs or parking costs for a daily commute and driving the car for trips outside of that.

          Overall we simply need to plan to achieve less VKT travelled by any vehicle using fossil fuels. End of story.

          Not just horse trading of some cars for some motorcycles or mopeds.

        7. I’m fully aware of the acc levy making up the majority of the cost of small motorcycle and moped rego fees. I mentioned that in my comment above.

          “While I’m sure some people would drive a moped instead of a car.

          The reality is that many would still have a car as well – using the motorcycle or moped for its cheaper running costs or parking costs for a daily commute and driving the car for trips outside of that.”

          I’m reading yes this would lower carbon emissions (and help other city issues), but not in the way that you would like. A car kept in the garage isn’t as good as no car, but its significantly better than a car daily driven. And I don’t see how having a moped increases the likelihood that people still own a car (in fact the opposite is probably true). I’m not saying we should stop all the other city improvements (cycling/walking/pt etc) on the contrary, the humble moped improves these too. I know I’d rather cycle around mopeds than cars. Anything that decreases the weight and volume moved around on roads is great and giving people more options to do so / improving these options is good too.
          The clean car feebate thing is stupid and shouldn’t be applied to anything, however bicycles don’t pay $163 a year (plus a carbon tax on the fuel) and run on the same roads, arguably with more risk. I dont think we should charge bicycles, but I also dont think $163 a year makes sense either. $50 perhaps

      2. Unfortunately not. The current carbon price in the ETS of $35/tonne is only adding 7c/litre to petrol. Not enough to make any change, not even if it tripled.

        The Clean Car Standard (fuel efficiency) will do a bit better but it’s going to be very slow. The 105gCO2/km average doesn’t kick in until 2025 (assuming the government goes ahead with what was proposed last year) so you could image total fleet emissions halving by 2040 or so. That’s way too late.

        It also assumes the fleet doesn’t grow any more and doesn’t solve all of the other problems caused by cars.

        We do need the fuel efficiency standard but it’s just one piece of the puzzle.

        1. If it costs 35$ per tone to sequester then ¯\_(ツ)_/¯. seems pretty reasonable to me. They do need to remove the ceiling though. Probably best to do it over a couple year period to make sure it doesn’t totally flame the economy, like if there is a price spike and fuel prices double or triple over a week or 2. The price ceiling is just too much manipulation imo, you want to make a free market, then let it do what its supposed to do.

    2. What chance that emissions could be tested at the tail pipe for WOF with the result being a factor in the charge for the registration. If this were sufficient it could change the face of our vehicle fleet. Allow a period of notice with a stated increasing charge over time so that the road users could adjust their emissions according to their budget. This (I feel sure) would influence the new vehicle buying and lead to increased rate of change to our fleet.

      1. Tail pipe testing is used to reveal compliance with air quality emissions standards rather than carbon emissions. Of course in NZ, being clean, green etc etc we don’t need to do that sort of commie nonsense, a bit of smoke here and there doesn’t hurt and anyway the wind will get rid of it.

      2. …except we already require vehicles to comply with emissions rules on entry certification (not that they couldn’t be tuned up a little) and seeing as we don’t make any cars here, that’s the easiest way to shape new vehicle purchases.

        As for exhaust testing, I’m not sure everyone driving around in a 20 year old Corolla that has done hundreds of thousands of kms is going to have the capacity to ‘adjust their budget’ to pay even more to register a car they probably won’t replace as long as it runs.

        1. Lots of NZers drive 20 year old Corollas. They would not pay more to continue driving their gas guzzlers.

      3. Great idea. They have this in the UK except it’s based on vehicle model. For 2017 vehicles and onwards the rates increased by 2-3 times to the following annual registration fees. This gives some idea of what is required to effect change.

        CO2 sample vehicle
        0g/km Nissan Leaf £0
        1 to 50g/km Outlander PHEV £10
        51 to 75g/km Merc, BMW PHEV £25
        76 to 90g/km Yaris hybrid £110
        91 to 100g/km Prius hybrid £135
        101 to 110g/km Camry hybrid £155
        111 to 130g/km Honda Fit £175
        131 to 150g/km Ford Focus £215
        151 to 170g/km Ford Mondeo £540
        171 to 190g/km Honda Odyssey £870
        191 to 225g/km Outlander £1,305
        226 to 255g/km Ford Territory £1,850
        Over 255g/km Commodore V8 £2,175

        1. The political problem is NZ’s vehicle fleet profile is rather different to that of the UK and the average carbon g/km is much higher. At the moment, some of the worst offenders incredibly get a tax rebate. They also top the sales figures.

        2. Zippo, don’t you think NZ is in that situation exactly because we haven’t done as they have in the UK? UK has had registration fees linked to emmisions for 3 decades. Enough time to shape the entire fleet twice over.

  6. It’s be nice to see this blog do a post about the benefits of Lake Onslow Pumped Hydro Scheme. This scheme has the ability to radically change our emissions landscape by making our electricity 100% renewable and lowering the cost of power (and hopefully driving the uptake of EV and other users).
    Fingers crossed that not only does it go ahead but that they go for the bigger full capacity option of 12,000GWh storage.

    1. I’ve been following this project for a while and I’d really love to see it go ahead. Hopefully it makes economic sense. It would be good to see a few other smaller pumped storage schemes be investigated. Nearer to wind and solar, and load centers. Some of Aucklands volcanic cones could be decent for such a scheme especially combined with plenty of rooftop solar. But I doubt that would ever in anyone’s wildest dreams be allowed to go ahead. Pumped hydro storage is IMO the best storage solution for NZ compared to batteries anyway. Similar efficiencies, purely mechanical, no chemistry, heaps of renewable potential in wind and solar to fill them up, can run forever unlike actual hydro dams.

        1. I can’t think of anywhere in the North Island that would be nearly as good in terms of storage potential. The line losses would be relatively minor when compared with the amount of storage this scheme would allow.

        2. Yep. In the current grid makeup, it makes some sense to have it there I think. However in a future grid it might not make any sense.
          If most of the power is coming from the hydro lakes down in that area then the power is essentially going past there anyway and there is no real transmission loss penalty to storing it. However it wouldn’t make sense to regularly send ample solar and wind power from the north island down to be stored, and then sent back up to be used. On the other hand, if its the only good geography for large pumped hydro in the country then whatever, better than batteries.
          Like I mentioned previously, hourly fluctuations on solar and wind are probably best handled up north in much smaller instillations. But dry windless spells are going to need some heavy lifting for potentially a large part of a year.

        3. Zippo – it’s actually in a great location as the transmission infrastructure is already in place. In a dry year when it is used, the other hydro dams won’t be used much. Alternatively if it is being used for wind base load backup then again the other hydro won’t be being used much.

          But yes another pumped hydro scheme somewhere in the upper North Island would be useful. Perhaps in the Coromandel Ranges or even down in the King Country.

        4. I don’t think there are any potential pumped hydro sites in the North Island with anything like the capacity of Lake Onslow.

      1. Yes, but as Jack said you can convert other emissions to electricity reducing the overall emissions. Cut transport in half, cut dairy factory and other heavy industry. Electrify more of the rail network etc.
        Onslow (with associated wind power increases) could reduce our emissions by around 25% (or more) within a decade.
        Also another benefit is reducing our foreign fuel bill by billions each year.

        1. I think that further electrification of the economy can largely be supported with more intermittent renewable generation (largely wind power) and the existing hydro lakes. Lake Onslow means that we don’t have to rely on gas to buffer the intermittent renewables generation in the odd dry year when the existing hydro lakes cannot do that job.

        2. @sherwood We could rely on wind and solar with no Onslow but it would increase power wastage from renewables once our existing hydro dams are committed. As they have to maintain min flows and only have so much storage. We would end up with water spilling, and turbines shutting down on surplus days. There is a tradeoff to be had as with anything, squeezing every drop out of the existing generation with heaps of storage would likely be much more expensive than just building a few more turbines. As more wind is wasted, the economic viability of these farms decreases too which would slow investment significantly. The question is, is the government better off subsidizing the storage infrastructure, or subsidizing the generation, (or penalizing pollution) From an operations point of view, probably better to have the govt / transpower running Onslow. I personally think this would be better, then again, I’m for some reason really attached to the idea of the project being built. Having some gas generation imo isn’t the end of the world, so long as it wasn’t used more than once a decade say.

        3. Yes I said it’s probably a good project, I just think we should keep the benefits in perspective.

  7. Thanks for an interesting post. One challenge is that the focus on averages eg for households at a certain distance or level of affluence is that is ignores within group variation. The one study on this that I am aware of – from Adelaide in the early 2000s – suggests that within group variation is massive. This suggests there is a huge opportunity for change through peer motivation, social marketing etc.

    Unfortunately there is no longer an on-line link to this study. My own paper on Urban CO2 emissions, written in 2008 and quoting this research, noted that after controlling for income, age and household composition there was a 230 fold variation between the most energy intensive households in outer suburbs and the least energy intensive. For those in inner-city suburbs, with the same controls, the variation was 80 fold. Almost all of this variation was accounted for by transport energy use.

    Looking again at the second moment of data – variance – as well as the first moment – mean or media – can provide a richer picture of what is occurring. We see this is the graph of distance versus CO2 use above – the logarithmic curve is interesting but so is the very large variation around that curve at any given distance. Bringing the most energy intensive households down towards the mean at each distance can make a big difference overall.

    1. Some guys just like driving gas guzzlers. Like those who regularly go surfing at Piha because otherwise they will have to carry large surfboards by hand on non-existent PT.

      1. I guess the question is what will influence those “guys” to change? Because a lot of statistically identical guys are not. This would be a question of academic note only were it no for the fact that there are massive gains to be had from working out a positive answer 🙂

      2. Surfers are not really known for driving gas guzzlers. They’re much more likely to be seen in an underpowered 1.6L cheap station wagon.

  8. But don’t you think NZ is in that situation exactly because we haven’t done as they have in the UK? UK has had registration fees linked to emmisions for 3 decades. Enough time to shape the entire fleet twice over.

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