A DC charger with a car sitting on it for two hours after the session ended is not a charger. It is a parking space with an expensive object attached. Idle fees exist to fix that, and they are the most commonly misconfigured price on any charging network.
The confusion is about what the fee is for. It is not revenue. A successful idle fee produces almost no income, because the behaviour changes and the bay frees up. If your idle fee line is growing month on month, it is priced wrong or communicated badly — probably both.
Four parameters, and how to set each
| Parameter | Typical | How to decide |
|---|---|---|
| Grace period | 10-15 minutes on DC | Long enough to walk back from a coffee, short enough to matter |
| Rate | Above the local hourly parking rate | It has to beat the alternative use of the bay |
| Cap | Yes, always | An uncapped overnight fee is a refund request and a review |
| Overnight exemption | On AC, usually | Nobody moves a car at 3am, and nobody is queueing either |
The overnight exemption is the one operators forget. An idle fee that runs from midnight to seven on a residential AC charger punishes exactly the behaviour you want — plugging in and leaving it — and produces the worst kind of complaint, because the driver is entirely right.
Disclosure is most of the design
A fee the driver did not know about is a dispute regardless of how reasonable it is. Three touchpoints, all of them cheap:
- 01On the price screen before the session starts, alongside the energy rate.
- 02A notification when the session ends, saying the grace period has begun and when it ends.
- 03A second notification when the fee starts accruing. This one prevents most of the complaints on its own.
What it does to the host relationship
Idle fee revenue is usually shareable with the site partner, because the bay is their asset and the fee protects it. Say so in the agreement explicitly, in the list of what is in and out of the revenue base, or it becomes an argument the first time a month has an unusual number of them.
The measure of success
Not fee income. Median time from session end to unplug, before and after. If that number drops and idle income stays near zero, the fee is doing exactly what it was designed to do.