Fifteen minutes, twelve months

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Why a charge point gets designed around the evening

Most people approach charging as an energy question: how many kilowatt-hours, at what price, on which tariff. In Flanders that misses the component that moves most. Since January 2023 part of the distribution charge for customers with a digital meter is calculated from the monthly peak — the highest quarter-hourly average offtake in the month — and the figure applied is the average of those monthly peaks over the preceding twelve months, with a floor beneath it. A peak is therefore not an event, it is a liability with a twelve-month tail. Fifteen minutes in which a charger, an oven and a heat pump all pull hard together can shape a bill until the following year.

Once that is understood, the design question changes. It stops being how fast a charger can go and becomes how reliably it can be prevented from setting a new peak. Dynamic load balancing is the answer that actually works: the charger measures what the rest of the building is consuming and takes only the headroom, so the total stays under a ceiling. On the great majority of evenings nothing is perceptible, because nobody needs a car charged in forty minutes when it is parked for nine hours. Static limiting, which caps the charger at a fixed value without reference to the house, is a cruder version of the same instinct and still worth having. What neither of them is, is an optional extra to be sold afterwards.

Alongside the money sits a safety point of a different kind, less discussed and more consequential. Charging equipment can produce smooth direct residual current, and an ordinary residual current device of type AC or type A may not detect it — and may be impaired by it, so that it fails to operate on faults it would otherwise have caught. Protection for a charging circuit is therefore a type B device, or a type A device together with equipment detecting smooth DC residual current at six milliamps, which many chargers now integrate. The circuit is dedicated rather than shared. A quotation that mentions none of this is quoting a different installation from one that does, and it is worth asking which you are being offered.