What will the electric vehicle revolution mean for our electricity system?

Electric vehicle being charged

James Dixon
PhD Student, Electronic & Electrical Engineering
University of Strathclyde

16 November 2018

James Dixon is a PhD student researching the likely impact of electric vehicles on the electricity system – and how we might deal with it –  as part of the EPSRC Centre for Doctoral Training in Future Power Networks and Smart Grids based in the Electronic & Electrical Engineering Department at the University of Strathclyde.

The Implications of Going Electric

There seems to be a general consensus that the future of the private car is electric – National Grid estimate that we could see 36 million Electric Vehicles (EVs) in Britain by the year 2040.

As this transport revolution accelerates towards us – possibly at a rate of 0-60 mph in 1.9 seconds – we need to ensure we have an electricity system that is fit to handle the charging of all these vehicles.

Our basic requirements are in terms of energy (kWh) and power (kW) (i.e. the rate at which energy flows to the vehicle).

The energy question is relatively easy to answer. If we take current driving patterns as our starting point, we know that cars in Britain drove 409 billion kilometres in 2017. Given that an EV will typically use around 15-20 kWh of electrical energy for every 100 km it travels, we can say that if everyone drives around the same distance in the future as they do now, we would need to generate 60-80 TWh more electrical energy over the year (an 18-24% increase on last year) if we wanted to electrify 100% of private transport. Sure, it’s a big number – but it’s quantifiable.

The power question, on the other hand, is complicated. It depends upon when, where and how people will charge their EVs.

It is often stated that the vast majority of EV charging will be carried out overnight at home, supplemented with the occasional use of rapid chargers – say, at motorway service stations – while on longer journeys. However, there are problems with this.

The problems with at-home EV charging

Firstly, it’s not for everyone. 43% of UK households do not have off-street parking and therefore have nowhere to install a charging point. This statistic gets worse in urban areas; in Glasgow, 73% of dwellings are flats – the vast majority of which have nowhere to park a car. While some of this charging demand could be met with on-street charging facilities, such as using lampposts to support EV chargers, it is likely that this won’t be sufficient to meet charging demand if there are indeed to be 36 million EVs in the next two decades.

Secondly, it has the potential to cause significant problems to the existing electricity distribution networks. At-home chargers are located at the very ends of the electricity network where peoples’ houses are connected, and the system was not designed to handle this much power. In My Electric Avenue, an Ofgem-funded trial designed to enable investigation into the impact that charging clusters of EVs might have on local electricity networks at peak times, it was estimated that 32% of Britain’s electricity distribution network will have to be upgraded if 40-70% of people install domestic chargers.

These two problems become trickier when we consider how the system is paid for. The costs of network upgrades are currently shared amongst all energy consumers by ‘use of system charges’ included in our bills. These charges are based on our annual energy demand, not our peak power. But because networks are built based on peaks these charges actually have very little relationship with our impact on the need for reinforcements.

What this means is that if we’re not careful we could have a repetition of what happened with Feed in Tariffs and solar panels in the early 2010s – in that all energy consumers are forced to foot the bill for something that only benefits a small sector of consumers (in that case people with enough roof space for solar panels and enough bank balance to front the investment; in this case people with their own vehicle and access to their own off-street parking). As these individuals are likely to be the better-off on average, the uptake of EVs could end up disproportionately increasing the energy bills of the already fuel-poor without offering them any direct benefit.

A System Fit for the Future

When designing the network for the future of transport then, our approach must include:

  1. Widespread publicly-available charging infrastructure that enables those without their own off-street parking to be able to charge their EVs
  2. A way of paying for use of the electricity system that doesn’t penalise those without their own cars and/or driveways

It seems that the former is to some extent being addressed, with an average of 182 new charging locations appearing in the UK every month and a £400m Charging Infrastructure Investment Fund pledged as part of the UK Government’s Road To Zero publication to establish 14,000 public charging locations by 2040.

The latter, though, is perhaps more complicated. We could, for example, take inspiration from Sweden, where energy consumers pay their ‘use of system charge’ by an annual subscription based on their fuse size, which in turn sets the level of peak power they can draw from the network. There, if a customer wants to install an EV charger and use it at peak times, their supplier must install a larger fuse and the consumer must pay a higher subscription fee. Likewise, if a consumer wishes to pay a lesser subscription fee, they can do so by using energy more flexibly, reducing their peak demand and installing a smaller fuse.

This would incentivise those who can charge at home to spread their energy use over the time for which they’re at home – so-called ‘smart charging’ – which could then pave the way for matching EV demand to intermittent renewable generation – further helping the decarbonisation of the energy system.

Might this be a fairer way of funding an electricity system fit for electrification of transport? Of course, there could be unwanted outcomes from this – it could end up penalising those who already have high-demand appliances like electric heating and showers, which could then exacerbate rather than relieve fuel poverty, or it may end up deterring people from charging at home which would lessen the flexibility of EV charging – which currently stands to be of great value to our grid as it can absorb ‘excess’ renewable energy.

Of course, the issues are complicated and the argument is nuanced – I’m certainly not claiming to have all the answers. Something I have had to leave out of this blog post – not to be left out of the ongoing discussion – is the changing nature of transport itself (such as the advent of autonomous vehicles and increased use of car sharing services), and the impact this will have on our system design.

One thing is for certain: there’s plenty of work to be done.

The Centre for Energy Policy is currently exploring exactly these issues in our research project under the CESI flexible fund. Read the Research Brief "Modelling the Distribution of Costs from Network Upgrades for Electric Vehicles (EVs)"

Tags: Energy