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Free calculator

Use this calculator to

  • Convert a planned kW load into the kVA of supply capacity it will actually occupy
  • Size generators, UPS and transformers, which are all rated in kVA, from a kW load list
  • Check how close a new load will push your site to its agreed supply capacity (ASC)
  • Quantify how much kVA headroom power factor correction would release

kW to kVA Calculator

Convert real power (kW) to apparent power (kVA).

kW
PF
Result
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Formulas

  • kVA = kW / PF

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Common scenarios

Select one to run it in the calculator above.

For business

Why this matters for businesses

DNO connection applications are quoted in kVA, not kW, and the difference between the two on a real site can be 10 to 25 percent depending on the load mix and the power factor. A 400 kW production line with a 0.85 power factor needs 470 kVA of supply capacity, and the connection application has to declare the kVA figure honestly or risk the offer being reissued at a higher cost. Multi-site operators planning EV rollouts or heat pump retrofits have to walk through this conversion for every site in the estate.

The financial impact of getting it right shows up in two places. First, DNO connection charges scale with the kVA being applied for, and an over-stated application can cost five-figure sums in unnecessary reinforcement. Second, the ongoing capacity standing charge on the supply contract is set by the agreed MIC in kVA, and a site that has an inflated agreed capacity is paying that monthly fee for years before anyone questions it. A capacity audit across a 30-site portfolio frequently releases enough headroom to fund the EV charger install outright.

Purely Energy works with I&C and growing mid-market clients on capacity strategy for electrification, where the supply-side conversation runs in parallel with the engineering scope. The conversion between kW and kVA is the language the DNO speaks, the half-hourly data is the evidence base, and the contract is where the savings get locked in. Getting all three lined up is the work, and the calculator here is one of the inputs.

Common questions

How do I convert kW to kVA?

Divide by power factor: kVA = kW / PF. A 400 kW load at 0.8 power factor occupies 500 kVA of supply capacity, while the same load corrected to 0.95 needs only 421 kVA. Because power factor is always 1.0 or below, the kVA figure is always equal to or larger than the kW figure, never smaller.

Why do I need kVA when my equipment is rated in kW?

Supplies, transformers, generators and UPS systems are all rated in kVA because they are limited by current, and current follows apparent power. Your agreed supply capacity (ASC or MIC) with the DNO is set in kVA too. So to know whether a 90 kW kitchen or a 400 kW production line fits an existing connection, you must convert it to kVA at a realistic power factor and compare it with the ASC, not the headline kW.

What happens if my kVA demand exceeds my agreed supply capacity?

Half-hourly metered sites that exceed their ASC pay excess capacity charges under DCP161, applied to the kVA taken above the agreed figure in each month it happens. Repeated breaches are also a network risk flag with your DNO. If a planned load pushes the conversion above your ASC, the options are power factor correction, peak shaving, or applying to the DNO for an increase before the load is connected.

How do I size a generator from a kW load?

Convert the load to kVA at its power factor, then pick a set whose kVA rating sits comfortably above it; three-phase generator sets are conventionally rated at 0.8 power factor. Allow extra headroom where large motors start direct-on-line, since starting current can be several times the running figure. The conversion here gives the steady-state requirement; your generator supplier should validate the transient sizing.

Does improving power factor reduce the kVA I need?

Yes, and it is often the cheapest capacity upgrade available. The kW your processes need stays the same, but correcting power factor shrinks the reactive component, so kVA = kW / PF falls. Taking a site from 0.8 to 0.95 cuts the kVA demand of the same load by about 16 percent, which can pull a site back inside its ASC or release headroom for new equipment without a DNO application.

Related calculators

The conversions that procurement and engineering use alongside this one.

kW to kVA Calculator | Free UK Capacity Tool | Purely Energy