On Thursday we wrote a small story about a new phenomenon at EV fast-charging stations – big displays with the kilowatt hour pricing rate, just as we are used to see at petrol stations.
We noted that the pricing offered at that charging station in the Barossa Valley included a big discount for charging during the middle of the day, to help soak up excess solar in South Australia, a state that already sources a world-leading wind and solar share of 70 per cent over the last 12 months, and where rooftop solar can sometimes meet all of local electricity demand.
One reader pointed out that another fast-charger in the state – at Port Adelaide – has an even better offer: Free fast charging between the hours of 9am and 4pm.
The pricing at the Port Adelaide Plaza shopping centre was only recently changed, according to regular users (down from a day-time rate of 12c/kWh we believe) and is part of a series of trials in South Australia to test consumer response to various price signals.
Obviously, some users were delighted. “Free charging,” posted one Tesla Model 3 owner on the Plugshare app.
Actually, it’s not quite free. It has a time rate of 18c a minute, which means that at the full rate of 120kW it effectively costs 9c/kWh, if your car can charge that fast.
It also means that once a car’s battery goes past the 80 per cent limit, for instance, it’s rating of charging slows and so the effective rate on a time-based tariff goes up. It’s a good mechanism to encourage turnover on a busy charging station.
The morning and evening peaks – between 5am and 9am and 4pm to 10pm are subject to a pretty hefty tariff of 90c/kWh, while the rest of the time – 10pm to 5am – is 45c/kWh.
The fast charger uses ABB technology and is managed by Chargefox. The changes are being made as part of the South Australian Smart Charging Trial.
Note: This story has been updated to correct the tariffs, particularly the time of use tariff during the daytime. We blame the  punctuation on the notice, but it was a mistake all the same. Thanks to all the readers who pointed it out.
Giles Parkinson is founder and editor of The Driven, and also edits and founded the Renew Economy and One Step Off The Grid web sites. He has been a journalist for nearly 40 years, is a former business and deputy editor of the Australian Financial Review, and owns a Tesla Model 3.