What is maximum import capacity?

Maximum import capacity is the most power a site is contracted to draw from the distribution network at any one moment. It is agreed with the distribution network operator, recorded in kVA, and it sits on the electricity bill as a separate standing charge for each kVA per day. The figure describes an instantaneous ceiling rather than a total quantity of energy over the year.

Suppliers and network operators also call it agreed supply capacity or authorised supply capacity. The three terms mean the same thing.

How is maximum import capacity charged?

The charge is a daily rate for each kVA of agreed capacity, applied whether or not the site uses it. A site holding more capacity than it needs pays for the headroom every day of the year, so the agreed level is worth checking against what the site actually draws.

The rate varies by distribution region and by voltage. It is published in the network operator's use of system charging statement, and it appears on the bill separately from the charge for the energy itself.

What happens if a site exceeds its maximum import capacity?

Drawing above the agreed level triggers an excess capacity charge, usually applied to the highest half hour recorded in the month. In some regions the excess is billed at a higher rate than the ordinary capacity charge.

A site that exceeds its capacity repeatedly can also be asked to raise its agreed level, and the network operator can require reinforcement work before agreeing to it. Our analysis of import capacity breaches covers how often this happens on real half-hourly data and which half hours cause it.

Can maximum import capacity be changed?

The agreed level can be raised or lowered by applying to the distribution network operator. Lowering it is usually straightforward where the site's measured demand supports the lower figure, and it reduces the daily charge from the point the change takes effect.

Raising it depends on the capacity available on the local network. Where the network is constrained, the operator can quote for reinforcement, and the cost and the timescale both vary widely by location.

Solar generation and battery storage both change the picture, because they reduce the power drawn through the connection at the moments that set the capacity requirement. Lupa models that effect against a site's own half-hourly data, and the platform reports the capacity a site would need under each combination of solar and storage.