What is Authorised Supply Capacity (ASC) and why do we need it?

Authorised Supply Capacity, or ASC for short, is the maximum amount of power your site is permitted to draw from the grid during any half hourly period. For example, if you were in a busy period and had switched on lots of electrical equipment at the same time, you would be making good use of your authorised supply capacity!

ASC is pre-agreed with your Distribution Network Operator in the form of a connection agreement, likely signed at the time the supply was originally installed. Our energy grid is finely balanced, and the network needs to know how much power you are likely to need in order to have the required capacity available for you to use at any time. Exceeding your agreed capacity can lead to excess capacity charges, and should your excess damage the grid in any way, you could be liable.

ASC can also be known as kVa, Agreed Supply Capacity, Capacity Charge, Maximum Import Capacity, MIC, Availability, or a combination of the above! It is measured in kilovolt Amps (kVa) and is typically charged on your bill as pence per kVa per day (p/kVa/day), or pounds per kVa per month (£/kVa/month).

What is a typical capacity charge

Capacity charges vary from region to region and are dependent upon the type of supply you have coming into your property. For example, a low voltage half hourly may attract a capacity charge of around 5 pence per unit, whereas an extra high voltage supply may see charges of over 15 pence per unit.

The cost per kVa is only half the story, though; how much capacity you have available is just as important.

How is ASC calculated?

It's always a good idea to check you are being billed correctly for ASC. If you are looking to increase or decrease your capacity, you will need to know how to calculate the change in cost.

If you know your current available capacity and your capacity charge (which should be detailed on your bill or latest contract), use the formula below to calculate your charges:

Capacity Charge = Available Supply Capacity * Capacity Charge Rate (pence/kVA/day) * Number of Days in Billing Period

Example:

If your current capacity is set at 200 kVA, the unit capacity charge is 5.5p/kVA/day, and your billing period is 31 days, your calculation would be:

(120 kVA * 5.5p/kVA/day * 31 days) / 100 = £204.60 per month.

Can I change my Authorised Supply Capacity

Capacity charges can make up a significant part of your bill and as a fixed charge, they stay the same every month unless you do something about it.

Many are legacy values agreed upon when buildings were first completed and have no bearing on the business activities currently being conducted. It may be that the building was designed as a factory but is currently used for warehousing, or perhaps a renewable energy asset has been installed that may be pulling down peak demand.

In any case we often find that the ASC is no longer in line with peak demand and a review needs to be carried out.

Why change my Authorised Supply Capacity

Instant savings can be achieved by decreasing your ASC where it is too high, and also by making an increase where you are regularly exceeding your capacity and incurring excess charges. This all happens outside of your supply contract which remains completely unaffected by any changes you may make to your ASC.

Changing your capacity can also benefit the wider community and even the environment. By freeing up capacity on your local grid you reduce the necessity for expensive and carbon intensive upgrades that might otherwise need to be undertaken to make sure your neighbours and the local community continue to have enough capacity.

You may also enjoy further savings should your reduction be large enough to cause your energy supply to drop to a lower TCR banding. This would mean a lower standing charge at your next contract renewal.

Energy supplies are not re-banded automatically however, and you may need to contact your DNO or wait for the next re-banding period, which takes place every four years.

How do I change my Supply Capacity?

In order to change your capacity you will need to liaise with your distribution network operator to obtain historic maximum demand reports. Once these reports have been analysed a new maximum capacity can be determined and you will need to go back to your distributor to have them issue a new Connection agreement. Or if you prefer, contact the team at Clear Utility Solutions who are happy to do the hard work for you.