Best Public EV Charging Strategy: A Viewpoint

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Guest Contributor: A member of the e-zoomed EV Community

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Guy Turner has spent 30 years in the energy and environmental sector, working in senior roles in consulting, commercial research and infrastructure project development, most recently as Strategy and Analysis Manager at EDF Renewables. He has an academic background in engineering, economics and corporate finance and has owned a Renault Zoe for 9 months.

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Electric Cars: The Basics

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For those of you new to zero-emission electric driving, we recommend a read of the following articles:

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Charging Infrastructure – Fewer Big Charging Stations Or More Smaller Units?

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The government’s strategy to support the expansion of the EV market rightly highlights the important role of public charge points. Without ready access to charging points, drivers will fear they won’t be able to charge when they need it during a long journey (although this fear may be overplayed – see my previous blog on the subject of range anxiety).

In 2018, the UK Climate Change Committee recommended that the number of rapid chargers located near the major roads network needed to expand from 460 in 2016 to 1,170 by 2030, while the number of public chargers needed for ‘top-up charging’ needs to rise from 2,700 in 2016 to a staggering 27,000 by 2030. Whilst all expansion of electric car charging systems is good for the growth of EVs, it is questionable whether this huge increase in top-up public chargers will be the most effective way of providing the necessary charging infrastructure. One of the most important considerations for a battery-electric vehicle (BEV) driver when looking for a charging point is certainty of availability. 

From an EV driver’s perspective, the option of using dedicated rapid charging stations seems more appealing, even if they are fewer and farther between. Crucially they can provide higher certainty of availability due to the number of charging points and short residence times. With the fastest ultra-rapid 350kW chargers, a green car can fill up with 100 miles in around 7 minutes (if capable of taking this rate of charge). 

If the driver is in a hurry and this top-up is enough to get to the destination they will soon be on their way, freeing up the charging post for the next user. Even with the more common 120kW to 150kW chargers a Tesla would receive an 80% charge in 30 minutes. With a bank of say 15 chargers (typical of Tesla super charging stations), they could process a minimum of 30 electric vehicles an hour.  More likely though drivers would use these stations as rapid top-ups to grab enough charge to get them to their destination where they can charge more completely. If each vehicle stayed 15 minutes, a 15 bank charging station would be able to process 60 electric vehicles an hour. 

Bulk, rapid charging stations probably also make better sense economically than single point on street chargers. The cost of installing a 150kW ultra-rapid chargers is in the region of £100,000, including grid costs, or around £0.6 per Watt of charging capacity.  A much slower on-street charger of 11 to 22kW is likely to cost around £6,000 to install, or £0.3 to 0.5 per Watt.  

Even though the on-street chargers appear slightly cheaper to build per unit of capacity, the economics may work out better for the ultra-rapid chargers. This is for two reasons.  Firstly, if drivers use on-street chargers as long-term parking bays for their shopping or other errands, they could well stay beyond the useful charging period, taking up valuable charging time that could be used by other vehicles. Charging companies try to manage overstaying by increasing the tariff after a set time, but in practice this is still likely to happen.

Because on-street charging stations are slow, it means drivers will have to spend several hours to gain sufficient charge to make a difference to their journey. The intention of drivers in these situations is not to charge the vehicle, and then think of something to do: it is the other way round. Their first intention is to spend time at their destination – shopping, work, leisure etc – and if they can find a charging point, so much the better. If what they are doing runs over the allocated charging time, they are unlikely to return to their vehicle to move parking bays. Overall, the incentive is probably to overstay. 

In comparison, dedicated ultra-rapid charging stations are only used for the purpose of charging the vehicle. Drivers may well make use of the 15 to 30 minutes they have at the station, to grab a coffee, visit the toilet or do some essential shopping, as you would at a conventional service station. But once the driver has achieved the required charge, they are on their way and the unit is free to be used by the next customer.  

The second reason is that we humans value speed and convenience. The use of ultra-rapid chargers is priced at a hefty premium to standard electricity tariffs, 30-40p/kWh compared to an average home electricity of around 15p/kWh.  This is what we are probably willing to pay for filling up quickly with inconvenience to our journey. Incidentally, at around 40p/kWh is equivalent to filling a combustion engine car with petrol as current day petrol prices, so probably places a ceiling on what can be charged.

In summary, it looks like the combination of more intensive use and higher tariffs will make the ultra-rapid chargers the consumers choice.  Relatively slow on-street chargers will have their role too, but I suspect investment swing significantly towards ultra-rapid chargers in the near future. 

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