The NZ ambition to replace internal-combustion engines with electric cars

Ever wondered what’s inside the famous Tesla battery? More batteries. Thousands.

— by Dr Michael Kelly,
University of Cambridge, UK.

May, 2020.

Next time you stand for 90 seconds filling your petrol tank, you might think of the enormous energy flow. Chemical energy is entering your tank at typically 17 million joules per second, or a gigantic 17 megawatts.

That’s equivalent to the energy given off by 17,000 one-bar electric heaters (imagine 6 tennis courts covered in them) or 24 hours of average power consumption (24 kWh) for 700 New Zealand households. A full tank (about 1,500 megawatts) would run those 700 houses for three full months.

Optimistic champions of green obsession

It’s a lot of energy and causes many difficulties that are glossed over by optimistic champions of the green obsession with all-electric cars.

In making personal mobility all-electric, two important considerations must be weighed. The first is that electric motors convert electricity to motion three times more efficiently, in energy terms, than the internal-combustion engine does with petrol. The second is that we do not recharge an electric battery in 90 seconds.  The numbers are slightly different for diesel vehicles, but the main conclusions are the same as for petrol.

When electronics first became portable in the early 1970s, the battery was a carbon-zinc type. All the global research in the fifty years since then has produced a lithium-ion battery, which has six times the density of energy storage; but the energy stored in petrol is still more than forty times denser than this.

For direct comparability in performance, the car battery has to be forty times bigger in volume than the petrol tank. A Tesla car weighs 2.2 tonnes and its battery 540kg and occupies 400 litres:  for a high range of 600km, you would need 48 litres of petrol weighing 36kg.

Benmore could charge all our cars every 35 days

Consider Benmore Power Station, the second biggest in New Zealand, with a maximum generation capability of 540 megawatts. At full power, it could refill the batteries of 32 cars if they were to be charged in 90 seconds. Now that electric engines are three times as efficient at using electrical energy compared with cars using petrol, the energy from Benmore could actually charge 96 (say 100) electric cars in 90 seconds. Suppose instead we charge them over a period of 90 minutes, i.e., sixty times slower, which is more realistic but still very fast, we could then charge 6000 cars at once, or about 100,000 in a day. There are about 3.5 million cars and light vans in New Zealand, so Benmore could recharge the NZ light fleet every 35 days!

New Zealand uses ~37% of all its energy[1] on the transport sector, and the current total electricity capacity provides New Zealand with ~24% of its energy requirement[2]. If that transport energy was electricity rather than fossil fuels, the energy figure is divided by three to account for the extra efficiency of electric motors. For New Zealand to transition to an all-electric fleet for transport, we would have to use 50% of the existing electricity grid for transport, or enhance the existing generating capacity by 50% to cope with transport on top of every other demand.

We need 50% more power and grid capacity must more than double

Little of this extra electricity will be generated by hydropower as there is much resistance to more damming of New Zealand rivers. Any wind and solar used for transport will have to be produced and stored so that vehicles can be recharged on demand. I will say something more on large-scale batteries below. If there is an additional requirement to electrify heating and cooling of buildings the present grid would have to double in capability to handle both heat and transport. It is worse than that, as heat demand peaks in winter requiring as much as 6-8 times the dedicated electricity as used for cooling in summer.

In addition to extra generation and transmission capabilities of the grid, all the distribution from local substations will have to be upgraded. A typical NZ house uses about 24 kWh of electricity per day, averaged over the year, for an average usage of 1 kW peaking at 3-5kW at times of high demand. A typical electric battery charger draws 7 kW for slow charging over 12 hours or 15 kW for faster charging over 6 hours. So each household’s usage would surge by 7 or 15 times the long-term average when charging a car, up to 30 or 45 times normal for two or three cars.

This represents a significant fluctuation in electricity use. The local substations are guaranteed to fail at some point under this level of demand. Unless individuals are told when and where they can recharge their car batteries, there will be regular brownouts. In the UK if a supermarket wants to install say 4-6 charging points it must contribute NZ$0.5M to upgrade the local substation. The electrification of domestic heating would add further to this burden on the local grid.

The Elon Musk backup battery wouldn’t last a day

The further nail in the coffin of an all-electric transport system in New Zealand is the use of battery technology to handle intermittent renewable energy storage at the scale needed for cities. This is most easily seen with reference to the battery that Elon Musk installed outside Adelaide two years ago, at a cost of NZ$100M. Its capacity is encapsulated by two numbers, the energy stored, i.e., 130 MWh, and the maximum rate at which electricity can be drawn, i.e., 100 MW. In practice one does not fully discharge, or indeed fully charge a battery, and typical usage involves an 80% to 20% discharge of stored electricity.

To compare this, consider the energy back-up provided by gas and diesel generators for (say) Wellington Hospital: if its peak electrical demand is of order 5 MW (private communication), the Musk battery would last for about 16 hours at full power on that 80% to 20% discharge. After that we would need a new charged battery on the back of a dozen articulated lorries.

The diesel and gas generation would continue so long as there is fuel: the generators together would cost of order NZ$0.8M. One needs back-up of order a week to cover a modern equivalent of the 1998 blackouts in Auckland. The cost and performance differentials are very high (125:1 and 7-10:1 respectively), and will not be bridged by 2050 on current progress, let alone 2025 when Extinction Rebellion insist all will be in place. These differentials apply across the whole economy.

In the short term, doomed to failure

There is another battery issue regarding electric vehicle concerns. If we replace just the whole UK traffic fleet of today with electric vehicles (assuming they use the most resource-frugal next-generation batteries), it would make the following materials demands[3]:

  • 207,900 tonnes of cobalt – just under twice annual world production.
  • 264,600 tonnes of lithium carbonate (LCE) – three quarters of world production.
  • at least 7,200 tonnes of neodymium and dysprosium – nearly the entire world production of neodymium.
  • 2,362,500 tonnes of copper – more than half the world production in 2018.

The New Zealand requirements would be about a tenth of this. Indeed, it is estimated that the current electric vehicle battery manufacturing capacity would have to increase by 700-fold for all the world to be transported in electric vehicles, with vast increases in the supply of materials described above: way beyond known reserves. If there are shortages of batteries, cars will be idled and internal combustion engines taken out of mothballs on a large scale.

Put simply: the infrastructural engineering capability required to provide for electric cars and electric heating by 2050 is a massive and probably unachievable ambition. To attempt to accelerate it, to 2025, is madness. The rest of the world can look at New Zealand and choose whether to laugh or weep. One thing it shouldn’t do is emulate NZ. Elsewhere I have done the equivalent analysis for the UK[4].

Enthusiasts talk about their individual electric car, but never consider what infrastructure is needed when everyone else’s car is also electric.

Dr Michael Kelly is Emeritus Prince Philip Professor of Technology in the Department of Engineering at Cambridge University, Fellow of the Royal Society, former chief scientific advisor to the Department for Communities and Local Government, and Trustee of the Global Warming Policy Foundation.


[2] From Wikipedia sites, New Zealanders use about 8 MWh of energy per person per year, and the total electricity generated per year is 40,000 GWh, hence the figure just quoted.



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17 Thoughts on “The NZ ambition to replace internal-combustion engines with electric cars

  1. Rick on 09/05/2020 at 5:20 am said:

    Thank you, Prof. Mike Kelly, for doing the crucial arithmetic which our green saviours of the world are unwilling and apparently unable to do, in spite of the fact that it’s not particularly hard arithmetic and well within the capability of most senior high school maths students.

    It is, though, the extensive, laborious and time-consuming kind of arithmetic that visionary leaders of grand social movements with no time to lose never get around to doing before they launch and prosecute their great world-changing revolutions. And because they never take the time and make the sustained effort that are needed to do their sums properly and plan their enterprise thoroughly in depth and detail, it inevitably crashes on the physical technicalities which they have casually overlooked, disdained and ignored.

    As I understand it, the great green vision is of an ideal world where all humanity lives in perfect harmony with the natural environment and all civilization runs solely on ‘clean’, ‘renewable’ energy flowing bountifully and everlastingly from the Sun and the Earth’s core. I have no criticisms to make of that romantic vision. But, as Professor Mike’s sobering arithmetic demonstrates, it is a vision which cannot possibly be realised with current, state-of-art renewables technology.

    Perhaps it will become possible one day, maybe with the Star Trek technology of the 23rd or 24th century, but at present it is not possible and therefore anyone who tries to make it happen with today’s technology is doomed to fail. It would be like building a bridge to the Moon: only someone who has never thought about the technical issues involved would even think of trying it. But when it comes to converting humanity’s global energy infrastructure to run on a new, futuristic technology that hasn’t been invented yet, the green movement throws caution to the winds, bulls straight ahead and tries to bamboozle every government on earth into committing the nations to doing it – in short order, too!

    That is insane. As Prof. Mike’s arithmetic makes clear, the green project is certain to fail, probably with disastrous consequences for most people now living too. But the greens are deaf to warnings and blind to the foreseeable consequences of their intended actions. I think the world needs saving from these mathematically, scientifically and technologically incompetent world saviours before it needs to worry about the unproven man-made climate emergency from which they claim to be saving us.

    • Brett Keane on 09/05/2020 at 8:28 am said:

      This being a standard of their work. Its foundation even:

      Neil Ferguson and Mann are now being put in the same box (and their products buried, dare we hope?).
      Brett Keane

    • Richard Treadgold on 09/05/2020 at 12:33 pm said:


      Harry had many justified complaints. Can you say who’s talking about “Neil Ferguson and Mann … now being put in the same box”?

    • Brett Keane on 10/05/2020 at 2:57 pm said:

      RT, I know it looks like ‘party-pooping, but Harry came up in my researches, and I decided to place his good judgment where it belongs. Right near the base of the UEA boondogle. So our trolls know we really have them by the short and curlies, and how stupid they are. Let our laughter, the best medicine, echo down their corridors forever…..
      From Brett, who supports the Wayback Machine plus his Stats Professsor. Plus those great Canadian calculators of odds re endless hockey sticks from random numbers.
      Harry, too, was wondering if he had stumbled on a Rock Colledge coding exercise…….

    • Rick on 10/05/2020 at 12:34 am said:

      Hi Brett,

      Ah, yes, the infamous HARRY_READ_ME file from the ‘Climategate’ tranche, exposing the incredibly chaotic real nature of the ‘science’ behind climate change alarmism. Poor Harry, I wonder what became of him – I fear he may have died of apoplexy from trying to make coherent sense of that huge jumble of amazingly incoherent climate records.

      I gather that Prof. Ferguson’s epidemiological model is in the same genre of quasi-scientific mumbo-jumbo too. As one programme analyst* observed:

      “Due to bugs, the code can produce very different results given identical inputs. They routinely act as if this is unimportant.”

      Unimportant? I doubt that the hundreds of millions of people (at least) whose lives have been turned upside down by Prof. Ferguson’s code would agree that its misleading indeterminate output is ‘unimportant’.

      And since we aren’t allowed to see Mann’s primary data, no-one can tell what kind of a mess his ‘science’ might really be in.

      But I don’t doubt there are many more who should go in the same box (labelled ‘Crackpot lefty academics with delusions of grandeur and no scientific validity’). Unfortunately, though, they seem to be running everything as the de facto rulers of the world at the moment. I hope enough people will survive their reign of chaos and terror to rebuild human civilization after they have trashed it as they seem to me intent upon doing.

      [*See: ‘Code Review of Ferguson’s Model’ by Sue Denim at ]

    • Mack on 10/05/2020 at 10:50 am said:

      Speaking of climate-gate and corrupt “scientists”….here’s an interesting character whose not afraid to point them all out….
      Here’s his list of the “Hall of Shame”….
      Pretty well covers the main offenders.

  2. Richard Treadgold on 09/05/2020 at 11:28 am said:

    As you say, the great green vision cannot be realised with the technology they suggest, the climate emergency is not in evidence and our attempts to achieve it cannot but fail. The arithmetic is irrefutable and the result is clear. It won’t work in the UK and it won’t work here.

    • Richard, just recently I hit upon a link to hopenothate,org and noticed a list of “promises, demands” and such like. It’s a bit frightening, really. Maybe the multi-billionaires have too much money and keep setting up these groups for a bit of a laugh. It seems to me they also control a lot of blogs; the majority of blogs, for all I know. The words madness and insanity become increasingly appropriate to describe what is on offer through the mainstream media, on the internet or the other net.

      Still reading Nietzsche, now The Gay Science, may I take the liberty and quote a bit from Book Five, page 335. “Above all, one should not wish to divest existence of its rich ambiguity: that is a dictate of good taste, gentlemen, the taste of reverence for everything that lies beyond your horizon”.

      It may be said that the climate activists and their pseudo-scientific backers provide rich ambiguity, but it is in the service of an overwhelming push to override and flatten everything not supportive of its dystopian narrative.

  3. Simon on 10/05/2020 at 5:29 pm said:

    Not a bad article from Michael. The straw-man of course is that nobody is proposing a conversion of 100% of the vehicle fleet. Electric makes much more sense for commuting and then preferably for small vehicles. Where the revolution is occurring is in e-bikes and electric skateboards etc, the amount being sold of these is extraordinary at the moment. You usually do not need to be enclosed in a square box if you are only travelling a few kilometres.
    We have been driving a PHEV for six years now and it has been great. No pollution and zero maintenance. Short distance travel is by push bike or Onewheel (

    I overlooked this comment earlier. I’d like to give Michael the opportunity to respond, if he sees it. – RT

  4. Mack on 15/05/2020 at 11:42 pm said:

    The little AA battery picture reminds me of this ad…

  5. Cambridgedon on 19/05/2020 at 1:09 pm said:

    Interesting, the fossil fuel industry receives subsidies to the tune of $5 trillion a year.

    So apart from survival, economic sense to go with the science.

    The job of an engineer is to solve engineering problems. Or give it to people who can. “Too hard” is a “Fail”.

    • Richard Treadgold on 19/05/2020 at 4:04 pm said:

      More like 500bn, actually, but they’re not subsidies, you silly rabbit. All businesses are allowed tax breaks on their costs, like Foodstuffs, Bunnings, Zespri, Watties, Fletchers, Amazon, Apple and the All Blacks. You only call it a subsidy when you’re talking about oil companies. Oil companies enable all those other businesses to do business. Stop them, you stop everything. If you don’t believe me, take a look at the effects of the shutdown/isolation/quarantine. No business, no development, no smoke and fumes, no pollution, no carbon dioxide, no income. No education, no sports, no visiting. I don’t see the point of your engineering ‘too hard’ remark.

    • Cambridgedon on 19/05/2020 at 5:51 pm said:

      No, wrong, nothing to do with usual business practice of not paying tax on expenses.

      From the Oxford Dictionary online:

      1A, sum of money granted by the state or a public body to help an industry or business keep the price of a commodity or service low.

      This paper updates estimates of fossil fuel subsidies, defined as fuel consumption times the gap between existing and efficient prices (i.e., prices warranted by supply costs, environmental costs, and revenue considerations), for 191 countries. Globally, subsidies remained large at $4.7 trillion (6.3 percent of global GDP) in 2015 and are projected at $5.2 trillion (6.5 percent of GDP) in 2017. The largest subsidizers in 2015 were China ($1.4 trillion), United States ($649 billion), Russia ($551 billion), European Union ($289 billion), and India ($209 billion).


      The International Monetary Fund recently updated its comprehensive report on global fossil-fuel subsidies. It arrives at a staggering conclusion: In 2017, the world subsidized fossil fuels by $5.2 trillion, equal to roughly 6.5 percent of global GDP. That’s up half a trillion dollars from 2015, when global subsidies stood at $4.7 trillion, according to the IMF. If governments had only accounted for these subsidies and priced fossil fuels at their “fully efficient levels” in 2015, then worldwide carbon emissions would have been 28 percent lower, and deaths due to toxic air pollution 46 percent lower.

      The report suggests a morally grim situation: As the planet careens toward climate catastrophe, governments are forking over trillions of dollars—one-fifteenth of the global economy!—directly to oil, coal, and gas companies. But the challenge of combatting climate change through politics is much more difficult than some tidy math can make it seem. This calculation suggests that recalibration would be simple. If we only cut those subsidies, then carbon pollution would plunge, and we’d be much further along in addressing the climate challenge.


      American oil and gas companies were often in financial trouble well before the coronavirus economic crisis, and now many are asking for taxpayer assistance to cushion their fall.

      Texas-based Battalion Oil, which recently changed its name from Halcón, has taken a $2.2m coronavirus relief loan, after going bankrupt twice within the last four years and facing accusations of excessive spending on an executive pay, private planes and luxury vehicles.

      Despite a history of financial woes, Battalion is receiving assistance under the paycheck protection program (PPP), the US government’s strategy for getting cash to small businesses so they can continue to pay workers during the coronavirus shutdown as part of a more than $2tn aid package. The company will not have to return the money if it spends it on approvable expenses, including payroll, rent and utilities.

      Many independent drillers were already mired in debt from chasing the fracking boom, according to analysts. They were finding it harder to secure investment and even facing bankruptcy.

    • Ergo, a propagandist linguistic sleight of hand, backed up by ah, not lies, to be sure, not damned lies either,…let me think…

    • Richard Treadgold on 23/05/2020 at 12:33 pm said:

      Cambridgedon, you say,

      No, wrong, nothing to do with usual business practice of not paying tax on expenses.

      But it is, it’s exactly that. I know what subsidies are, but when activists such as Greenpeace, Oil Change International (OCI) or other anti-industrial agitators calculate these “subsidies” they employ an extraordinarily broad meaning of the word that does include ordinary tax exemptions. Essentially, a subsidy is however they define it. Here’s what OCI say about it:

      A fossil fuel subsidy is any government action that lowers the cost of fossil fuel energy production, raises the price received by energy producers, or lowers the price paid by energy consumers. Essentially, it’s anything that rigs the game in favor of fossil fuels compared to other energy sources.

      The most obvious subsidies are direct funding and tax giveaways, but there are many activities that count as subsidies – loans and guarantees at favorable rates, price controls, governments providing resources like land and water to fossil fuel companies at below-market rates, research and development funding, and more.

      That reveals their deep bias against fossil fuel companies.

      A Scoop story, Greenpeace has it wrong – no subsidies for oil and gas, shows Greenpeace is also biased on the topic.

      It’s a fair bet that business activities comprise the lion’s share of a company’s business expenses, and explains why the numbers you quote are so high. But it’s nothing to do with some extraordinary generosity extended only to fuel companies. The figures are crooked.

    • Cambridgedon on 19/05/2020 at 6:17 pm said:

      There is a problem with the formatting on this bog.

      I think if you refresh the page it comes right, but let me know. – RT.

    • Barry Brill on 24/05/2020 at 8:54 pm said:

      Refresh didn’t fix

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