kVA (kilovolt-ampere)
kVA is the unit used to size your electricity supply and, for bigger sites, to charge for capacity.
What it is
A kilovolt-ampere (kVA) is a unit of apparent power: the total load your supply has to carry, including power that does no useful work. Its cousin kW measures the useful part. The ratio between them is called the power factor, a number between 0 and 1, so kW = kVA × power factor. A perfectly efficient load has a power factor of 1; motors and some lighting pull it lower.
Where you will see it
- On bills for larger or half-hourly sites as an agreed or "maximum import" capacity, with a daily capacity charge.
- On the paperwork for a new connection or supply upgrade.
- In the contract, if there is a charge when you go over the agreed figure.
Why it matters
Capacity is something you pay for even on quiet days, and exceeding it can bring extra charges. Many small shops and offices never see a kVA line, because their charges sit inside the standing charge. If you do, it is worth checking that the figure suits your real peak. Our guides on supply capacity and kVA charges and what a kVA charge on your bill means explain how to review it, and what happens if you exceed it.
Example
A workshop with a 100 kVA supply and a power factor of 0.95 can deliver 100 x 0.95 = 95 kW of useful power. If its busiest moment only ever draws 50 kVA, it may be paying for more capacity than it needs. Capacity reductions are arranged with the network operator, so the first call is to your supplier.
Related terms
Common questions on this topic
Sources
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.