Supply capacity

Supply capacity, also called agreed capacity or availability, is the maximum amount of electricity your connection is agreed to carry, measured in kVA.

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What it is

Supply capacity is the maximum electrical demand your site's connection is set up to deliver. It is measured in kVA (kilovolt-amperes). It is agreed with your distribution network operator (DNO) when you are connected, and can be raised or lowered later by request.

Where you will see it

Usually on half-hourly metered sites, as a line on the bill for an "availability" or capacity charge in pence per kVA per day, as part of distribution charges. Your contract or bill may show the capacity as "agreed supply capacity".

Why it matters

You pay for the capacity you hold, whether or not you use it. If it is far above your real peak, you may be overpaying. If your peak goes above it, you may get extra charges and, in the worst case, supply problems. Read about it in supply capacity and kVA charges and what happens if you exceed it.

Example

Illustrative figures. A site has 150 kVA agreed but its highest demand over the year is 80 kVA. If the capacity charge were 4p per kVA per day, the unused 70 kVA costs 70 × £0.04 × 365 = £1,022 a year. Reducing to, say, 100 kVA (leaving a buffer) would save 50 × £0.04 × 365 = £730. The rate is an example, not a published tariff, so ask your supplier or DNO for the real one.

Check peak demand over a full year before asking to reduce, and allow for new equipment such as EV chargers or heat pumps.

See kVA, kW, DUoS and three phase.

Common questions on this topic

Sources

  1. Business Energy Deals: reactive power charges (commercial explainer)

Related reading

General information only. Energy prices, rules and supplier terms change; check the latest position with your supplier, Ofgem or the Energy Ombudsman before you act.