Vehicle-to-grid (V2G) charging could reduce drivers’ electricity bills by more than £500 per year, a new study has found, but only if they keep their vehicle plugged in for most of the day.

The report from the not-for-profit consultancy Cenex says the savings will be much less for electric vehicles (EVs) that spend more time unplugged.

As part of the study, Cenex modelled a sample of 60 EVs, which were assumed to be plugged in for 28 per cent of the time on average. This figure is broadly in line with the typical charging behaviour of current EV drivers.

With smart charging alone, the average saving compared to unmanaged charging was £110 – £98 coming from lower power prices and £12 from the provision of grid services. V2G charging reduced electricity costs by an additional £16 and generated a further £94 of grid services revenues. This brought the total annual saving to £220.

Base case

Cenex also examined a scenario in which the model fleet was assumed to be plugged in for 75 per cent of the time. In this case, the total saving was £511, of which £414 came from selling grid services. Smart charging alone saved £75 and V2G charging an extra £436.

“If V2G is to provide significant value above savings provided by smart charging, then it is important that grid services are accessible as additional revenue streams,” the report concludes. “Without this any additional upfront cost of V2G will likely negate savings.”

“For V2G, the key driver of this grid service revenue is the plug-in rate. With current EV plug-in rates at low levels (around 30 per cent), it will be important to encourage behaviour change to increase these rates.”

High plug-in rate scenario

The research highlights the importance of one particular revenue stream – frequency response – to the economic case for V2G charging. Halving the price for frequency response reduced the total saving by £54 – or almost a quarter – when compared to the base case.

And it warns the move to half-hourly electricity settlement is likely to offer little in the way of additional savings. The base case assumed EVs were charged on an Economy 7 tariff. Moving them onto a half-hourly tariff only shaved £4 off the average electricity bill.

The report says the findings suggest EVs used within council fleets or as a second household car are among those which will be best suited to V2G charging.

Cenex chief executive Robert Evans said: “While there has been an increasing focus on vehicle-to-grid charging, until now there has been a lack of clear data on its costs and opportunities, holding back the ability of organisations to build effective business cases.

“This report is the first step to bridging this information gap, and it shows multiple use cases where V2G delivers additional revenues and value above smart charging, especially around grid services. By making this information available Cenex aims to support the increased uptake of low emission vehicles and thus accelerate the move to a zero-carbon future.”