This is part of a series on electric vehicles (here are parts 123 and 4). It’s been 18 months since the last post – I feel like George R. R. Martin, except no one has really been asking me about when the next post is coming. Sorry, anyway, and I promise to get better. Today, I’m looking at the impact of these vehicles on NZ’s power supply. Again, I’ll abbreviate plug-in hybrid electric vehicles to PHEVs, and battery electric vehicles to BEVs – these are the “full” electric vehicles which don’t have an engine for backup.

In part 2 of this series, we saw that EVs are much more energy efficient than “conventional” cars. But instead of the established infrastructure for supplying and fuelling petrol, we’re going to need to rely on our electricity networks. Can the power grid cope?

The government’s Energy Strategy, written in 2007, argues that “switching to electricity as a fuel for our vehicles would make the most of New Zealand’s abundant renewable electricity supplies, particularly if transport was not competing for supply at times of peak demand”.

New Zealand’s car fleet travelled 39 billion kilometres in 2014. If the fleet was entirely replaced by BEVs using 20 kWh/ 100 km, it would require 7,800 GWh of electricity. That’s 18% of New Zealand’s 2014 electricity generation.

This might seem like a fair chunk of our nationwide electricity, and it is. But that analysis assumes that every car in the country is replaced by a BEV running only on electricity. In practise, it will take years or even decades for EVs to become firmly established in the market, and PHEVs – which will probably outnumber the “pure” BEVs – will only use electricity for part of their travel, running on petrol or diesel the rest of the time.

Tesla’s Model S. Fully electric, multiple award winning, apparently pretty damn cool, but like other EVs pretty damn expensive. Seen here in its natural habitat of overlooking scenic mountain valleys. Source

Additionally, the power companies have scoped out a large number of new plants (mainly renewable – wind and geothermal) which they could build in the future. The only reason they aren’t building them already is that electricity demand has been flat for the last few years. So the industry has plenty of room to boost supply to meet any new demand from electric cars (a number of academic studies have reached the same conclusion).

Overall, the power grid can certainly handle New Zealand’s car fleet being partially or even entirely replaced with electric vehicles.

Feeding power back to the grid?

Potentially, PHEVs and BEVs could even feed power back into the grid. The idea is that during low-demand times – e.g. in the middle of the night – EVs will charge their batteries, and then they’ll stay plugged in and send power back the other way during high-demand times. In theory, this could help to smooth daily fluctuations in power demand, i.e. the daily peak/ trough cycle. At least one paper (Smith, 2009) suggests that EVs could actually reduce New Zealand’s requirements for new diesel and gas peaker plants (which only run during high or “peak” demand periods) as a result.

However, there are a number of issues with using electric vehicles to provide “security of supply” for electricity. These include the slow charge/ discharge times for vehicle batteries, and the energy losses involved in transforming the battery’s energy back into electricity.

The biggest issue is that in New Zealand, our main “security of supply” concerns are for dry years rather than daily demand cycles. Half of our electricity generation comes from hydro, and the problems arise when there’s low rainfall and the lakes and rivers supplying the power plants are depleted. EVs won’t help with this problem, and I tend to agree with Clive Matthew-Wilson that “the times and situations when [advanced vehicles feeding electricity into the grid] would be of much practical help would be few indeed”.

This is a NZ-specific issue, so for most countries EVs may be much more useful for feeding power back to the grid. Even in New Zealand, our power generation profile will change over the next few decades, with wind (and maybe solar) becoming more important. The output of wind and solar plants tends to fluctuate, and EVs that can feed electricity back to the grid would be an excellent complement, smoothing out these variations. This could help us kick our dependence on fossil-fuelled electricity – the main advantage those plants have in NZ is that they can scale their production up or down quickly as demand changes. I’ve written previously that New Zealand can get to 100% renewable electricity even with current technology, but better power storage would only make that easier. Batteries for homes, like Tesla’s Powerwall, would help too, although as for EVs there’s a long way to go before they’re cost competitive.

Even in New Zealand, there are advantages to charging EVs outside of peak times; this allows for better use of existing grid capacity. Schafer (2011) cites two studies which suggests that if EVs are charged off-peak, they won’t have much effect on New Zealand’s electricity demand or the need for new power plant capacity. This will of course depend on the number of vehicles, and an all-electric car fleet would probably require some level of increase in capacity. The key takeaway from this post, though, is that the electricity market can definitely handle EVs, even if uptake is fairly rapid.

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  1. As you mention EV charging fits helpfully into the electricity use pattern because NZ’s peak electricity draw coincides with the evening driving peak [ie most EVs will be driving not charging at this time]. There is now a lot of certainty about this as we know that current EV users charge mostly overnight at home, with some work place top-up, and in fact fairly low use of other charging points. And this is likely to be reinforced by the steady range increase in new models coming through. So for NZ in particular EVs look like great distributed storage especially for intermittent electricity generation, especially wind [that stuff blows at night].

    Additionally the Bluff Smelter is nearing the end of its life and its associated Manapouri power plant generates around 15% of NZ’s supply; the power cos are desperate for some new demand of scale to arrive in time to absorb the likely addition of this source to the general market. The transport market is the only market of scale on the horizon, until perhaps someone comes up with a scheme for massive data centres in Dunedin or similar. NZ is profoundly well placed to electrify all of its transport systems, especially the spatially efficient urban Transit ones [Train, Buses, even ferries]. Especially as the capacity to add even more renewable generation as this transition occurs is huge. There is little technical problem with both expanding supply and replacing the last 20% of non-renewable generation in NZ with renewables.

    The challenges are regulatory and financial. However a well designed Carbon Tax or a real Carbon Trading Scheme would provide the necessary market signals and mechanism for this necessary and inevitable transition. I assume this is obvious to our Energy and Transport Minister but presumably the same grey and backward focussed men in the cabinet that delayed the CRL are preventing the obvious action here too. So many wins; just outside of their conceptual scope….?

    1. It does seem Patrick that Bluff Smelter may stick around for sometime in an operational capacity, even if that capacity is vastly scaled back.
      The reason is that if they close the plant fully they have to fully remediate the site back to how it was pre-smelter, and the costs for that, are a bit like those for cleaning up Nuclear power plant sites – uncertain up front – but known to be costly.

      Also the renegotiated deal that the Smelter got with Meridian for Manapouri’s power means it doesn’t have all its possible capacity covered under the new contract with Meridian, leaving the likelihood of a scale back but not full closure of Bluff smelter even more likely.
      That fact and coupled with annual [domestic at least] electricity consumption falling year on year, the glut of electricity will only get higher over time, so any shortfall of supply is less likely for renewables.

      And that also ignores the likely impact of domestic solar which is now getting down to competitive levels [especially if those usurious line charges are factored in to the costs equation]. which like EVs will eventually have a part to play.

      1. Yes the power cos are facing a difficult demand environment. No wonder they are desperate for more incentives to accelerate EV uptake. I do think the gov is right to be wary of can incentives on vehicles however, because of the likelihood of ‘middle-class capture’ but a real Carbon Tax based on emissions would be less distortionary, and more effective. Use the market!

      2. I think domestic solar (which is still a couple of years from being economic in most of NZ, though it makes sense in Australia) will change things, and tip the balance further. But it must be supported with adequate feed-in tariffs. Not the kind that mean domestic suppliers are being given retail rates, but the kind that mean that they get the equivalent of what a southern hydro generator is getting. This allows that excess of supply from the south to be used to balance dips in solar or wind supply, and to provide overnight charging to NZ’s increasingly electric vehicle fleet.

        We kind of have an oversupply, but if the next government decides to get serious about climate change (I believe they will), then we’ll need a little new generation, and different kinds of regulation that allow us to arrange supply and use in a sensible way.

        No doubt there will be some losers, and these losers will cry loudly in public as they always do. So I hope we get some good funding of public service broadcasting at the same time, to balance the sadness.

        1. Distributed solar in Australia is a complete no brainier now. Obviously the sunny climate is good, but also the peak demand time, as is the case in all hot places, is the afternoon as everyone hits the aircon, this of course matches the highest productivity from your PV. Also you are displacing mostly coal fired stinkers when you harvest your electrons from the sun.

          Both my Australian domiciled brothers have now installed it, one [an engineer] has set up everything in his house to run at peak generating time, from pool pump to dishwasher to washing machine. He’ll no doubt eventually get an EV as well.

          This is from 2013 but shows how distributed solar just kills the peak demand in Aus cities; saving a fortune in centralised generation:

          More on Aus peak smoothing via solar:

          NZ is wind rich, we have the most productive land based turbines in the world [we knew it was windy here], but home solar will take off too. Some time ago I calculated it was a no brainer for any household without a mortgage, even without feed in tariffs. What is not paid to a power company is like getting tax free dividends; a lot better than money in the bank…. that math will be better now.

  2. Demand will be gradual as well – there won’t suddenly be ten thousand EVs in NZ overnight. The Tesla 3 is still a while off, and the American idea of EV “affordability” seems contingent on it having tens of thousands of dollars of tax credits attached, so God knows what the actual price of one would be in NZ.

  3. The figures for vehicle power consumption may need closer scrutiny, Tesla claim a 420km range. However, if you’re a bit of a lead-foot I believe that can be whittled down to not much more than 120km!

    1. The point here is that the trend is clearly in increasing range and declining cost. Because NZ is at the end of supply chain, and the fact that we buy heaps of secondhand cars, we won’t be seeing quantities of EVs here soon.

      Additionally even that extremely pessimistic figure of 120km is more than enough for almost all vehicle trips taken in NZ, and certainly all almost all urban ones.

      The question really is only about timing, this is a properly disruptive technology for the liquid fuels distribution trade and I expect it to follow an uptake curve like digital cameras replacing film cameras, eventually, but over a considerably longer timescale.

      Gas stations are photo labs: they will be gone, the only question is how long will it take?

    2. Tesla are working on cheaper cars still with decent ranges. Had the pleasure of driving the P85D and if anyone had any doubts before that about full EVs they were fully dispelled after that 0 to 100 is 2.8 seconds.

    1. For vehicles that have low utilisation, or intermittent use, electric could be a solution. I think it’s unlikely that we’ll get the energy density to have a long-distance high-use vehicle soon.

      However, in the meantime, hybrid vehicles are getting us much of the way. This NZ vehicle for example promises to reduce emissions and noise. I’d like to think that policy could support them, but for all Bridges enthusiasm for EVs it seems to be far away.

      1. Bridges is stymied by a story the Nats like to kid themselves about not intervening, or ‘picking winners’. The fact that they do it constantly doesn’t stopping them from using that line when they are faced with encouraging something outside of their usual list of approved beneficiaries: land speculation, pastoral farming, and extraction industries in particular. If you doubt this google ‘sexy coal’…

        Please everyone read the always insightful Richard Denniss, the chief economist at the Australia Institute, on government choices:

        And his latest little cracker, am becoming a bit of a fanboy of his style:

    2. Very true – the reason it’s “electric vehicles” instead is because that’s the common terminology in the PHEV and BEV acronyms.

  4. Interesting article, John. I’d like to contend, or at least comment on a few points points.

    1. As you say, there’s plenty of scope for NZ to generate sufficient electricity to power all vehicles.. an 18% increase over a decade is entirely do-able. From a generation and transmission perspective anyway. The challenges come with the local network. Even a small cluster of EVs in neighbouring houses could be problematic. An EV consumes about half the energy, but about the same peak demand as a typical household. But buying an EV isn’t subject to planning controls like building a house. And unlike the transmission system, there’s little or no means of control on the local network.. and yet active management will certainly be required to keep power flows and voltage levels stable. This is a profound challenge and very likely, the solution will involve customers’ participation.. smart charging controls, smart appliances, pricing signals. This in turn means residential (and commercial) consumers will gain a little more leverage over utilities and retailers: more choices, more power, in what is today an almost entirely one-sided relationship.

    2. At the same time, solar (and solar + storage) continues to head towards price parity. Outback Australia is already there, as are parts of regional Auckland too if you’re not already connected to the network. Even for large scale new developments in ex-urban areas generally, there will soon be a genuine choice about whether to even connect to the grid at all..

    3. In terms of EVs, this means their energy source need not reflect national generation mix; it can be entirely renewable and local. Even for EVs connected to the grid, whether here (where it’s already 80% renewable) or elsewhere, things are changing much faster than Clive Matthew-Wilson seems to suggest.. Saying that I agree with Clive’s central point that cars (EV or not) make little sense for mass transportation.

    1. Good point with the ‘local distribution’. I should have noted in the post that although EVs would only add 18% to the country’s power demand, they would make quite a difference to household demand. Households only make up a third of our power demand, so if they’re the ones who use and charge EVs the most, we could see quite substantial changes in the amount of power needed in a typical suburb, say. Again, that’s something that can be mainly taken care of with smart metering and off-peak charging, and perhaps the odd network upgrade in places. Given that this will only happen over a couple of decades, I’m sure the distribution companies will be on top of it.

    1. we do have a 2500 megawat array, but considering the location of our house, a quiet, unobtrusive windmill would be better and more effective in winter

    1. You can see gas taking the share of coal over the 90s and 2000s, and nuclear and hydro staying where they are. The 2010s wind boom is really evident, and if we had increasing demand we’d be seeing even more of it here.

      There are some surprises. It’s taken Hawaii, an isolated state with a lot of wind and sunlight, a long time to embrace cheaper renewables.

  5. A little bit off topic here but I can’t remember the study / report that was carried about sending West Coast rainfall over to the Canterbury side of the Alps. If drought and hydro generation are key to power prices I would think this is a relatively useful project to consider.

    If you damned an area say north-east of Mt Aspiring NP in the Landsborough river valley below Mt Hooker, you could run 2 pipes through the Alps to come out above Lake Hawea and Lake Ohau.
    2 pipes 5-10km in length would help service 5 lakes (Wanaka, Hawea and Ohau, Pukaki and Tekapo) and the various power schemes down stream and would help with consistency of supply as the West Coast is almost never in drought.

  6. Large scale wind turbines are only economic in very windy places. We have plenty more geothermal potential and a bit more hydro that can be developed far more favourably.

    Transmission lines from Manapouri north would be very expensive, and I don’t think NZAS will close anytime soon. Suddenly introducing an additional 15% capacity would not be good economically. It would be interesting to know what the most expensive 15% of our generation is, as unless it was essential for peaking capacity, it’d at least have to be mothballed. It’d probably close wind farms, at their next maintenance cycle.

    EV’s are available as Jap imports, e.g. Nissan Leaf. I was seriously considering one just prior to the fall in NZD. I think they will become popular for city dwellers doing short trips in stop start traffic, especially if our dollar strengthens again.

    With smart metering it will be easy to charge at night on cheaper off peak rates, which will help smooth total demand. I don’t think EV battery’s will be so much help for supplying back to the grid, as they’ll likely either not be plugged in or largely depleted for the PM peak. Batteries charged from solar installations would be good thou, I could see distribution companies offering more solar installation deals in future to take advantage of this.

    1. Bluff smelter won’t close for reasons I documented above but it will scale back its operations as each of the pot lines needs to be refurbished/reaches the end of their economic life, they will be shutdown permanently. Thus reducing Bluffs electricity demand.
      This will in short order release a large chunk of Manapouri power to the market whether Meridian like it or not.

      So they can either ship the surplus power north – for whatever they can get, loses and all, or they let the water run through the spill tunnels without making power from it.

      Which decision would you reach if you were Meridian?

    2. NZ is – by global standards – a very windy place. Large scale wind turbines are most certainly economic in many parts of NZ. Which is why wind currently generates more than 5% of NZ’s electricity demand. Yes geothermal is more at ~20%, but it’s also a more established technology. A large number of wind projects would be viable at wholesale electricity prices that are not much higher than they are currently.

      Far more problematic is 1) consenting requirements, especially landscape designations and 2) access/costs of transmission.

      1. Stu is right. NZ is perfect for wind generation. Trust Power’s Tararua farm runs at 43% efficiency, way above the average 30% generally expected.

        This is a windy-as place, as if we didn’t know that, what’s more the best sites are largely covered in grazing land, a perfect fit for turbines; it doesn’t force out the current use, but gives the land owner a new and constant income plus new access roads.

        The only reason more aren’t being built now is because of the weak market demand, and the shadow that Manapouri casts over the market. Insulation, LEDs, and other efficiencies are adding up to a soft market. Hence the power cos enthusiasm for EVs. But not so much for distributed generation of course.

  7. Anthony, I agree with you. Smart technology is starting in earnest and with the introduction of Telsa Powerwall – battery power ( and Vector Energy introducing and is marketing Powerwall in NZ ( and coupled with Vector planned EV charging stations through out the greater Auckland region, opens up the market for EV’s. It will not be long, for the other Power Co’s start doing the same. I noticed TV commercials for from some companies offering home solar and wind turbines installations. If a house has both solar and wind turbines connected to a Tesla Powerwall, that would make a house a stand alone electricity generating station where any surplus can be sent back to the national grid. I read in Stuff an article concerning the business version of Powerwell – If the Mega battery system can be fitted with solar and wind generation as will as national grid, would help in keeping NZ’s green image. The same principal can apply to Mega Battery System, that any surplus power can go back to the national grid. If every house in NZ was a standard alone electricity generating in until, then power co’s will not have the need to invest in expensive solar and/or wind farms. Existing hydro, geo-thermal and wind farms would provide the continuity of electricity back up.

  8. One possible way of electrifying NZ’s urban public transport is to try this technology from South Korea. It is the engineering that is new – the scientific principle of electrical induction has been around since Faraday in the early 19th century – and is featured at

    This should be required reading for all those Wellington Regional Councillors who have an aversion to overhead wires and want to dismantle the entire Wellington city trolley bus overhead system and replace it with DIESEL!!! Hybrid buses.

    1. Its not new tech, other countries are trying similar ideas, but as the article says:

      “One expert said it was likely to be a long time before South Korea’s more ambitious design became commonplace. “I think we are decades away from even thinking about a nationwide network of electrified roads,” said Ashvin Chotai, managing director of the Intelligence Automotive Asia consultancy. “For now, it appears to be more of a showcase technology than something which has the potential to be commercialised.””

      So don’t hold your breath for this to be rolled out anytime soon.

    2. Professor John Boys has been a proponent of inductive energy transfer for more than 20 years. I can remember it from when I was at Uni and I’m not even an electrical engineer.
      Efficiencies have certainly got a lot better but for practical use in transport (ruggedness/durability and clearances) I don’t know if its good enough to justify the cost of lost energy. I’ve had an inductive charger for a Nexus 7 tablet since sept 2013. It works great & is convenient but its only a few cents of energy.
      In the case of my inductive stove, it is more efficient and is controllable similar to gas.
      Its certainly a technology that is becoming increasingly more common.

  9. No one is predicting at 100% EV fleet anytime soon (if ever), ICE vehicles will be around for decades in one form or other, but over time they will be increasingly marginalised.

    Your comments re EV Battery capacity and life span and replacement costs, may be true today, but they won’t apply in the foreseeable future (foreseeable meaning sooner than driverless tech being commonplace).
    The same comments you make on EVs now all applied to early ICE cars once as well, they needed new engines every 100,000 miles or so.

    No one today expects their car engine [if maintained correctly] to last less than the life of the vehicle, in the future same will apply to EVs. So replacement battery costs will be irrelevant.
    As for capacity issues, no one expects to “fill up” their petrol cars when visiting unless on a long distance drive. And for that you use filling up places (aka petrol stations).
    In the future there will be the same sorts of facilities for EVs to fill up too. And don’t forget people need rests and filling up too so it can work for both car and occupants.

    Just like their aren’t petrols stations everywhere, there won’t be or need to be charge up points everywhere either. People currently charge at home because its convenient (and often cheaper) for them to do so.
    But its not a given that they will always do so. Once EV battery capacity reaches the distance a ICE car can go today (About 700km on a tank) then those issues pretty much disappear.

    Hydrogen is not the answer to anyones transport problems except the liquid fuel distribution industry. And they push it because they think it works like petrol does now.
    Only its way more difficult to make, transport, store and refill your car with than either electrons or fossil fuels.

    And as its turned into electrons to make the car go the entire fuel cycle is inefficient, to make it efficient you have to cut out the “middle man” of hydrogen and just use and store electrons directly.

    The US leader in Hydrogen for cars is California, and guess what? While you can buy (or more accurately lease) Hydrogen Fuel cell (FCV) cars today in California there, the number of filling stations that you can “top up at” is massively short of the planned rollout as mandated by California laws. Seems they’re finding its simply too expensive and hard to get the license to operate such stations and thats with the state government actively pushing it. So anyone with a FCV is not going to be able to drive it very far from their local hydrogen filling station right now, or for some time to come. Thats hardly very inspring or practical for the fuel thats going to take over the world according to you.

    it just seems that Hydrogen as a transport fuel is very much (still) a solution looking for a problem – for anything beyond Airships, Apollo Moon Rockets and Space Shuttles.

    Once there are a few Hydrogen fuel caused vehicle incidents, its appeal and acceptance by the wider public for a transport fuel will rapidly diminish.

    1. Not so sure Ari, well it depends how long you can hold them. Short and medium term demand looks to be affected by technology and efficiency gains, as well as the decline of big industrial users, including Tiwai Pt. Then there’s the very real threat of distributed generation taking hold. However longer term the electrification of transport certainly offers an new market sector. The really interesting question is, as ever, is about timing…?

  10. I think that “feeding back to the grid” will not take off. It would be silly for anyone sacrifice limited charging cycles to do “their part”, without little if any benefit… I think what’s more likely, is introduction of peak demand pricing for electricity – just like The Lines Company in King Country has started recently – this is now possible due to a roll-out of smart meters. That pricing model encourages smart(er) power usage – and it’s already kind of happening in the other parts of the country with the ripple-controlled hot water, off-peak (night) pricing plans, and even special plans just for charging electric vehicles overnight. So I think we can expect these kind of moves from the electricity companies rather than feeding power back from personally owned batteries.

      1. Sounds like a plan, but.. …problem is that the price of the electricity is only a small part of the fee we pay as part of our electric bill… ignoring the day charges, which you can’t escape, the unit (kWh) price for standard user consists of:

        * spot price (anything from 1c-40c, averaging around 10c)
        * network (transpower & lines): 6.32c
        * Electricity Authority: 0.113c
        * retail margin 1c – 20c

        so if you bought cheap rate at say 3c spot price, you’d pay 12c per unit. And if you sold it during the late afternoon/evening peak for 8c (that’s what it sells currently around the peak demand). You’d be making a 4c loss plus using up your battery charge cycles – and that’s completely ignoring the all the inefficiencies of converting the energy – that could be around 70% just a guesstimate.

        During a spike you might actually make some money, and spikes happen around 1% of the time, so it’s definitely a gamble with a rather high chance of losing! And to make it worse, the electricity retailers don’t have to buy your power, and some currently offer you a fixed 6c per imported unit irrelevant of time. So we’re a fair way of battery storage exporting to the network being a reality.

        sources – see for more detail:

      2. ‘sell it back at the peak rate’ – if current solar contracts are anything to go buy, the power companies will buy back your power at peak for less than they will sell it to you at night.

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