What is a kVA charge on my electricity bill?

kVA stands for kilovolt-ampere, a measure of the total electrical capacity of your connection. Your network operator reserves that capacity for you and charges for it at rates that vary by region and voltage, and your supplier passes the cost on as a line on your bill.

Where you will see it

Capacity charges are mainly found on larger sites with half-hourly meters. Look for "capacity charge", "availability charge" or "kVA" on the bill, shown as a rate per kVA per day multiplied by your agreed capacity. Many small shops and offices on standard meters don't have one.

kVA versus kW

kW is the real power doing useful work; kVA is the total power the supply must be able to carry. The two are linked by power factor. For example, equipment doing 80 kW of work at a power factor of 0.8 needs 80 ÷ 0.8 = 100 kVA. Motors, pumps and older lighting tend to have poor power factors. See kVA, kW and reactive power.

Agreed capacity and excess charges

Your supply capacity is set when the supply is connected. You pay for it daily even when you use little. If your demand goes above it, you can face extra charges for the excess, and the network operator may ask you to increase your agreed capacity. The exact charging rules vary by network operator, so ask yours. See what happens if you exceed your capacity.

Worked example

Suppose your agreed capacity is 175 kVA but 12 months of half-hourly data show a peak of 87 kVA. A consultancy case study used these figures and reported a saving of about £1,000 a year by trimming capacity. To see how it works, take an illustrative rate of 3p per kVA per day (not a real tariff) and cut capacity to 100 kVA:

• Reduction: 175 − 100 = 75 kVA
• Annual saving: 75 × £0.03 × 365 = £821.25

How to reduce it

1. Pull 12 months of half-hourly data and find your peak in kVA.
2. Compare it with the agreed capacity on your bill.
3. If there is a persistent gap, ask your supplier or broker to request a lower capacity from the network operator.
4. Leave headroom for growth; setting it too low risks excess charges.
5. Consider power factor correction to lower the kVA you need.

Check any one-off costs and whether increasing capacity later would mean a new connection charge before cutting.

Who should check this

It's worth checking if you have a half-hourly meter, have recently scaled down (closed a wing, removed machinery, fitted LED lighting or efficient equipment) or bought a site that was previously busier. Capacity set for the old use may be far more than you need. If you expect to grow, factor that in, because raising capacity later can involve network operator work and cost.

Next steps

Read our guide to supply capacity and kVA charges, and see whether a three-phase supply applies to you.