Flexible EV charging prices prove to be good for solar soak, and it stopped ICEing

A South Australian study into EV driver behaviour has found that pricing charging stations correctly in the middle of the day can help soak up excess energy in the grid and help stop ICEing behaviour by keeping the spot busy enough to stop incidents.

The study was one of nine commissioned by the South Australian government’s Department of Mines and Energy investigating different aspects of driver behaviour across the state to address concerns about the perceived impact of EV charging on the grid.

With the high penetration of rooftop solar and other renewables across South Australia, and the gradual increase in EV drivers on the state’s roads, it has been argued that charging could be used to help “soak up” excess power generated at peak times in the middle of the day.

Researchers considered whether changing the price at the charging station could influence the behaviour of drivers in any way, which could then be used to encourage more charging at peak times.

The study, conducted by fast-charging network operator ChargeFox, was among the first to begin and involved monitoring the way drivers used a DC fast-charging station at Port Adelaide Plaza in Adelaide’s western suburbs.

Over the course of the trial, researchers monitored activity at the station and interviewed drivers to better understand their decision making.

Miles Menegon, lead researcher at the company, said that the study initially assumed, based on other research the company had undertaken, that price would not make much difference on driver behaviour.

Past work suggested that “early adopter” EV drivers at that time tended to be middle aged men with disposable income who did not factor the cost of charging when making their decision.

“Over the course of the study, which was many months long and over a series of different experiments we ran, we found, surprise, surprise, price did have an impact,” Menegon said. “There were caveats, though: you can change pricing to encourage drivers to charge at different times of day, but they have to be the right driver.”

Menegon said EV drivers fell into two broad categories; “need to charge” drivers who will pay what they need to keep themselves on the road, and “want to charge” drivers who can choose when to charge usually because they can do so at home.

The researchers found that the second category, those with the ability to choose, perform a “mental arithmetic” when they leave the house.

This involved a calculation using a rule of thumb that considered variables such as how much they pay to charge at home, how much they thought it had cost to install the public charging station, the distance of travel and what else they might do while they charged, like go to a café or get groceries.

As a result of this, researchers were able to identify what they called a “goldilocks zone” that was lower than the cost of petrol, but did not give the power away for free.

When the price approached the same or higher than the cost of petrol, Menegon said drivers grew angry as they felt it disincentivized people driving electric vehicles, but when it was given away for free, they assumed the station would be unavailable as everyone was trying to use it.

“It’s like a honeypot. All the drivers will go there and it’s inconvenient, nobody wants to wait for a charge,” Menegon said.

The researchers who monitored the site also looked for instances of ICEing – that is where a petrol car, whether intentionally or not, is parked in the charging bay, preventing it from being used. As the charging-station was in a busy suburban carpark near an Australia post, it was frequently blocked by delivery vans prior to the trial.

“When we incentivised drivers to come charge during the middle of the day, and the chargers were being used regularly, that ICEing behaviour almost completely disappeared because there was activity,” he said.

“We talk about, read a lot about ways you can disincentive icing. One of the best ways to do that from these studies is to make sure your charges are very busy all the time so you don’t have a parking spot to actually park in.”

The South Australian Department of Mines and Energy was contacted for comment but did not respond by publication.