kVA Charges Explained: How to Stop Overpaying for Capacity

The capacity charge hiding on your half-hourly electricity bill, why so many businesses overpay, and how to bring it down safely.

kVA Charges – Look closely at a half-hourly electricity bill and you will find a line that has nothing to do with the units you used. It is charged in kVA, it turns up every month whether you trade flat out or sit idle, and most businesses pay it without ever questioning the figure. These are your kVA charges, and for a lot of sites they are quietly too high.

The good news is that kVA charges are one of the easier costs to fix. Unlike wholesale prices, which you cannot control, this is a number you have largely set yourself, often years ago, and it can usually be adjusted with a phone call and a bit of analysis.

What kVA Charges Actually Are

kVA stands for kilovolt-ampere, the unit used to measure apparent power, which is the total electrical capacity your site can draw at any instant. When you took on a half-hourly supply, your distribution network operator agreed to reserve a set amount of capacity for you. That reserved figure is your agreed, or authorised, supply capacity.

kVA charges are what you pay to keep that capacity available. The network operator levies a rate per kVA, applied to your agreed capacity every day regardless of how much electricity you actually consume. Reserve 500 kVA and you pay for 500 kVA, even in a quiet month when your real peak never came close.

This is separate from the energy charge for the kilowatt hours you use. kVA charges are about the size of the door, not how often you walk through it.

Why So Many Businesses Overpay

The usual problem is a mismatch between agreed capacity and actual demand.

Capacity figures are often set when a supply is first connected, then never revisited. A factory might have requested generous headroom for equipment it planned to install, machines that were later downsized, made more efficient or never bought at all. The agreed capacity stays put. The kVA charges keep coming for headroom nobody uses.

We saw exactly this on a recent client site. The agreed capacity sat at 175 kVA while the genuine measured peak across a full year never passed 87 kVA. Half the reserved capacity was dead weight, and trimming it back removed roughly a thousand pounds a year from the bill for no operational change whatsoever.

The Penalty for Getting It Wrong

There is a trap on the other side, which is why this needs analysis rather than guesswork.

If your demand exceeds your agreed capacity, you pay excess capacity charges, typically at a higher rate, and the network operator can reassess and force your agreed figure upward. Push past it repeatedly and you may trigger a connection review. So the goal is not simply to cut the number as low as possible. It is to set agreed capacity just above your true maximum demand, with a sensible safety margin for growth and unusual peaks.

That balance is the whole point. Too high and you waste money on kVA charges. Too low and you risk penalties and a forced increase.

Power Factor and Reactive Power

There is a second reason a kVA figure can run high, and it is more technical. kVA measures apparent power, while the useful work is measured in kW. The ratio between them is your power factor.

Sites with a lot of motors, pumps, transformers or older lighting often have a poor power factor, which means they draw more apparent power, and therefore need more kVA, to do the same real work. Reactive power like this can also attract its own charge on the bill.

Power factor correction equipment fixes much of this. By improving the ratio it lets you do the same job within a smaller kVA envelope, which in turn lets you reduce your agreed capacity and your kVA charges. For motor-heavy operations the payback can be quick.

How to Bring kVA Charges Down

The method is straightforward, even if the detail takes care.

Start with twelve months of half-hourly data and find your genuine maximum demand in kVA. Compare it with the agreed capacity printed on your bill. If there is a clear, persistent gap, there is a saving. Your supplier or broker can then request a reduction in agreed capacity with the network operator, and the lower kVA charges flow through from the next billing cycle.

It is worth treating this as part of a wider review of your non-commodity costs, the network and policy charges that now make up well over half of a typical electricity bill.

Done properly, capacity right-sizing sits alongside battery storage and demand-side response as one of the practical levers for cutting peak-related cost such as Red band DUoS charges, and it feeds directly into smarter energy procurement decisions.

Getting Your kVA Charges Reviewed

For most businesses this is found money. The analysis takes an afternoon, the change costs nothing to request, and the saving repeats every month for the life of the supply.

Catalyst reviews kVA charges and agreed capacity as a routine part of bill validation for the sites we manage, flags where capacity is overstated, and handles the request to the network operator on your behalf. If you have a half-hourly supply and have never checked the figure, ask our team for a review.

Related service: Non-Commodity Costs, how Catalyst helps businesses understand and reduce the charges hidden in their energy bills.

Further reading: TNUoS Charges Explained breaks down the transmission side of your network costs, which rose sharply in April 2026.