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kVA and Capacity Charges: Are You Paying for Headroom You Never Use?

Agreed supply capacity is set once and rarely reviewed. Getting it right can cut hundreds off a half-hourly electricity bill.

25 June 2026 7 min read

What agreed supply capacity means

Half-hourly sites reserve a maximum demand with the distribution network, measured in kVA. You pay a monthly charge for that reservation whether you use it or not. It is usually set when the connection is installed and almost never revisited.

Finding the gap

Pull twelve months of maximum demand data and compare the peak to your agreed capacity. A site holding 200 kVA but peaking at 110 kVA is paying for 90 kVA of nothing, every month.

Reduce carefully

Leave a sensible margin — typically 10-20% above historic peak — and account for planned equipment. Exceeding your capacity triggers excess capacity penalties, which are considerably more expensive than the saving.

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