Home chargers are sold in amps because a home supply runs at one fixed voltage, so current alone tells you the power. A DC fast charger feeds each car direct current at that car’s own battery voltage — and cars differ: many packs run at around 400 volts, others at around 800 volts, so the same current delivers roughly twice the power to one car as to the other. Kilowatts — volts × amps — is the rating that stays true for every car.
Key Takeaways
- Home charging quotes amps because the voltage is fixed; DC fast charging quotes kilowatts because it is not.
- Kilowatts are volts × amps — the only rating that stays true across 400 V and 800 V cars.
- A post’s kilowatt figure is its ceiling; your car’s ceiling and battery level decide the actual rate.
Why Home Charging Talks About Amps
At home the voltage is settled first: a Level 2 circuit in North America runs at 240 volts, so current times 240 gives the power. Current is also what the wiring must carry, so it is the figure installers plan around — and under the National Electrical Code, charging is a continuous load, so the breaker is sized at 125% of the charger’s current.
| Charger current | Breaker size (125% rule) | Power at 240 V |
|---|---|---|
| 32 A | 40 A | About 7.7 kW |
| 40 A | 50 A | About 9.6 kW |
| 48 A | 60 A | About 11.5 kW |
Why a Fast Charger Cannot Quote One Amp Figure
A DC fast charger converts AC to DC inside its own cabinet and sends DC straight to the battery, bypassing the car’s onboard charger — the core of how DC fast chargers work. That output’s voltage is set by the car’s battery pack, not the charger. What the charger and its cable do limit is current: connectors and cables carry a maximum amperage, and the highest-power cables are liquid-cooled for that reason.
The output is therefore a moving product — a voltage chosen by the car, a current capped by the hardware — and the only figure that survives both is the product: kilowatts. At a 500-amp cable ceiling:
| Situation | Voltage | Current | Power delivered |
|---|---|---|---|
| Same cable ceiling, 400 V car | 400 V | 500 A | About 200 kW |
| Same cable ceiling, 800 V car | 800 V | 500 A | About 400 kW |
| A 150 kW post, 400 V car | 400 V | About 375 A | 150 kW |
| A 150 kW post, 800 V car | 800 V | About 188 A | 150 kW |
The last two rows make the point: the same 150 kW session runs at completely different currents depending on the car. An amp rating would change with every vehicle.
What the Kilowatt Rating Does and Does Not Promise
The kilowatt figure on a post is the charger’s ceiling, not a promise to your battery. Your car has its own maximum charge rate and never accepts more than that; the session runs at whichever ceiling is lower, and it tapers as the battery fills, which is why charging slows down after 80%. The U.S. Department of Transportation puts the DC fast band at 50–350 kW, adding roughly 180–240 miles of range per hour at full pace — context for judging how fast a DC fast charger really is for your car.
Current still matters on the DC side — it moved into the hardware ratings. The EVDANCE JT08 NACS-to-CCS1 DC adapter is rated at up to 500 A and 1000 V: it passes through whatever post and car agree, so it is specified by the limits it must survive, not by a power figure.
One Charger That Is Rated in Kilowatts
The EVDANCE EV-RHDC30K-L is a compact DC fast charger rated at 22 kW, with OCPP 1.6J and an IP54 enclosure. Its rating is in kilowatts for the reason above: it will serve cars with different battery voltages, and kilowatts is the one figure true for all of them.
Frequently Asked Questions
Why is my home charger advertised in amps but a fast charger in kilowatts?
Because home voltage is fixed at 240 V, so amps alone define the power. A fast charger works across cars with different battery voltages, so only the product of volts and amps — kilowatts — stays comparable.
A post says 350 kW but my car charged at 150 kW. Is the post faulty?
Almost certainly not. Your car’s ceiling and voltage set what it can accept, and the rate falls as the battery fills. The post’s figure is its maximum, reached only by cars built to take it.
Can a charger push more current than my car accepts?
No. Car and charger negotiate the session; the car never accepts more than its designed limit, and the session runs at the lower ceiling.
Related Reading
- How Fast Is a DC Fast Charger?
- How Do DC Fast Chargers Work?
- Why Does EV Charging Slow Down After 80%?
- Level 1 vs Level 2 vs DC Fast Charging: A Practical Comparison
Sources & Standards
For buyers: EVDANCE is a DC fast charger manufacturer in Shenzhen — our 22 kW commercial DC charger, with samples before bulk orders.
