A year-long smart charging trial in South Australia has demonstrated that electric vehicle (EV) drivers do respond to time-of-use (ToU) pricing – but only when pricing is simple, clearly communicated, and aligns with their expectations.
The study, run by Chargefox and funded by the South Australian Department of Energy and Mining, tested different pricing strategies at a 120kW DC fast charger installed at Port Adelaide Plaza. The goal was to encourage drivers to shift charging behaviour to “solar sponge” periods (9am–4pm) when renewable energy is abundant and wholesale electricity prices are low.
The Experiment
Three pricing experiments were conducted over 12 months:
- Cycle One: Introduced extreme price variation – charging was $0.12/kWh during the day and $1.20/kWh in the morning/evening.
- Cycle Two: Prices were adjusted to a 5:1 ratio (e.g. $0.18/kWh during the day, $0.90/kWh during peak).
- Cycle Three: A new per-minute pricing model was introduced for the day period to reduce session time and increase throughput.
Session data was gathered via the Chargefox app, and qualitative insights were captured through surveys and interviews with EV drivers.
Key Findings
1. Drivers Can Be Nudged to Charge Smarter
The first two pricing strategies successfully shifted charging behaviour into the solar sponge period. In Cycle One, usage during the day increased by 293%, with a noticeable drop in peak period usage. Even when prices increased slightly in Cycle Two, this behaviour persisted.
“We observed that, contrary to our hypothesis, electric vehicle drivers were responding to our price signal and shifting their charge sessions to the ‘Renewable’ period,” the report states.
2. Simple, Per-kWh Pricing Works Best
Drivers preferred per-kWh pricing over per-minute models, which they viewed as unpredictable and unfair due to factors beyond their control, such as battery temperature or variable charging speeds.
In Cycle Three, when per-minute pricing was introduced, usage declined. Queueing reduced slightly, but this was attributed to lower patronage, not improved efficiency.
3. Drivers Apply a ‘Goldilocks’ Price Model
EV drivers gauge fairness based on a “mental model” of home energy rates plus a margin for infrastructure and convenience. Prices too high are seen as “gouging”; prices too low raise concerns about reliability and station availability.
There is a sweet spot. “Drivers want prices that are neither too high nor too low — the ‘Goldilocks zone’ — where charging is seen as fair and the station remains accessible and reliable,” said one participant.
4. Who Uses the Charger Matters
The trial identified two distinct user types:
- “Need to charge” drivers, with limited range or charging options, will pay any price to stay mobile.
- “Want to charge” drivers are more flexible and more likely to respond to price incentives.
It was the “want to charge” group that made the biggest behavioural shifts under ToU pricing.
Recommendations for Future Smart Charging Initiatives
The trial offers key recommendations for network operators and government bodies:
- Keep it simple: Use only per-kWh pricing with no more than four time periods.
- Charge for speed, not time: Drivers support a premium for fast charging but reject speed throttling.
- Don’t get too cheap: Extremely low prices reduce station availability and business viability.
- Add idle fees: These were well supported by drivers to prevent overstaying.
- Build with demand in mind: Two CCS2 connectors would have doubled the impact at Port Adelaide, where the single plug became a bottleneck.
- Focus on high-impact sites: Apply complex pricing strategies only where there’s a clear benefit, especially locations frequented by “want to charge” drivers.
The Bigger Picture
The project feeds into South Australia’s broader plan to make EVs the common choice by 2030 and the default by 2035, as part of a net zero transition. With a grid already powered by over 70% renewable energy and surplus solar power during the day, smart charging is essential to ensure the grid can handle growing EV demand.
Chargefox, now focused solely on software and network management, says the lessons from this trial are already shaping their pricing strategies.
“This research shows that we can drive behaviour change through price – but we have to get it right. The early adopters are willing to play along, but the next wave of drivers will need clear, tangible benefits,” the report concludes.