A commercial charger’s paperwork uses two different power units, and mixing them up undersizes electrical supplies. Kilowatts (kW) are real power — the rate at which energy actually reaches the cars. Kilovolt-amperes (kVA) are apparent power — the total the electrical supply must be able to carry. When the two numbers differ, the supply has to be bigger than the charging output alone suggests.
Key Takeaways
- kW is real power reaching the cars; kVA is the total the supply must carry.
- The power factor — kW divided by kVA, between 0 and 1 — measures the gap between them.
- Size supplies from the charger’s input rating in kVA, never from its kW headline alone.
- Some commercial tariffs measure demand in kVA, so the spec sheet figure can affect the bill.
Real Power, Apparent Power and the Ratio Between Them
On an AC supply, part of the current can run out of step with the voltage. That portion shuttles back and forth without ever reaching a battery, but cables, transformers and switchgear still have to carry it. Engineers therefore track the total as apparent power in kVA, and the useful part — the part that charges cars and appears on the charger nameplate — as real power in kW. The ratio between them is the power factor: the kW divided by the kVA, a number that runs from 0 to 1. The closer it sits to 1, the less extra capacity the supply needs for the same charging output. Modern charging equipment is built with power-factor correction to keep that ratio high, but the figure belongs on the spec sheet — ask for it rather than assuming it.
Where Each Unit Appears
| Figure | Unit | What it decides |
|---|---|---|
| Charger output rating | kW | What drivers get — for example, NEVI corridor chargers must deliver at least 150 kW per port |
| Energy billed | kWh | Metered energy: kW delivered over time, priced per unit on the tariff |
| Transformer and service size | kVA | The capacity the utility installs and the site can draw in total |
| Breakers and circuits | Amps at a stated voltage | Circuit sizing under the continuous-load rule: a 32 A charger needs a 40 A breaker, 40 A needs 50 A, 48 A needs 60 A |
| Charger input rating on the spec sheet | kVA or amps | What your supply must actually deliver when the charger runs at full output |
Reading a Quote Without Mixing the Units
The mistake to avoid is assuming a charger rated at a given kW needs a supply of the same number in kVA. The charger’s stated input rating already accounts for conversion losses and its power factor, so the supply is sized from the input figure, not the output headline. Work through a quote in this order: take each charger’s output in kW, ask the maker for its input rating in kVA, add the site’s other loads, then let your electrician and the utility confirm the transformer and service size against the total. Site planners make the same distinction when they size depots, as the fleet depot charging guide shows, and it is one of the quiet details behind how commercial charging stations are put together.
EVDANCE quotes output the way drivers use it: the EV-AC03201T dual-connector AC station delivers up to 43 kW shared across two connectors, and the EV-RHDC30K-L delivers 22 kW DC. For site paperwork, ask for each unit’s input rating in kVA alongside the output figure — the EVDANCE commercial charging team can supply both numbers for a quote.
Frequently Asked Questions
Is a 100 kVA supply enough for 100 kW of charging?
Not by default. The supply must cover the chargers’ input ratings, which include conversion losses and the power factor, plus the site’s other loads. Use the input kVA from the spec sheet, and let the electrician and utility confirm the service size.
Why do home chargers never mention kVA?
They are sold for a single circuit, by amps and kilowatts, where the difference is small and already inside the circuit rating. The gap starts to matter at commercial scale, where transformers, services and some tariffs are all sized or measured in kVA.
Can a poor power factor cost money?
Energy itself is billed per kWh, but some commercial tariffs also measure demand in kVA. On those tariffs, a low power factor raises the kVA demand recorded for the same kW of charging. Check how your own tariff measures demand before comparing equipment.
Related Reading
- How Do Commercial EV Charging Stations Work?
- Fleet Depot Charging: How to Size AC Chargers for Vans and Light Commercial Vehicles
- How Do DC Fast Chargers Work?
