Same headline number, different result. A 22 kW AC post delivers 22 kW only to a car whose onboard charger accepts 22 kW AC — most cars accept 7.4 kW or 11 kW, so the post idles at the car’s cap. A 22 kW DC charger converts power in the station, bypassing the onboard charger, so the same car can take up to the full 22 kW, limited by its DC acceptance and taper. That is why, at equal kilowatts, DC charges most cars faster.
Key Takeaways
- At equal 22 kW, the difference is the bottleneck: AC sessions are capped by the car’s onboard charger; DC sessions are not.
- For the 7.4 and 11 kW AC classes, one hour on 22 kW DC stores roughly three times and twice the energy of AC, before taper.
- Cars with 22 kW AC acceptance tie the comparison, and most PHEVs cannot use DC at all — classes, not slogans.
- Check your car’s two acceptance figures before choosing hardware.
Two Different Bottlenecks
On AC, the bottleneck sits in the car: the post supplies AC, the car’s onboard charger converts it, and its rating — commonly 7.4 kW or 11 kW, sometimes 22 kW — is the session’s ceiling. On DC, the bottleneck moves: the station converts, the onboard charger is bypassed, and the ceilings that remain are the station’s 22 kW and the car’s DC acceptance, usually far higher than its AC rating. Are EV chargers AC or DC? explains the two paths.
The Same Hour, Car by Car
Labelled arithmetic for one hour plugged in, allowing about 10% losses, before taper. The DC column assumes the car accepts at least 22 kW DC and arrives with room to take it:
| Car’s AC acceptance | Stored in 1 hour on a 22 kW AC post | Stored in 1 hour on 22 kW DC | Verdict |
|---|---|---|---|
| 7.4 kW class | About 6.5 kWh | Up to about 20 kWh | DC stores roughly three times as much |
| 11 kW class | About 10 kWh | Up to about 20 kWh | DC stores about twice as much |
| 22 kW class | About 20 kWh | Up to about 20 kWh | A tie — the car’s AC charger is not the limit |
Two cautions keep the table honest: DC tapers as the battery fills, so longer sessions narrow the gap; and a car whose DC acceptance is below 22 kW takes its own lower figure — the DC column is a ceiling, not a promise. Session times at the AC power levels are worked through in how long charging takes at 7 kW, 11 kW and 22 kW.
Why “Most Cars” and Not “All Cars”
- The 22 kW AC minority. Cars with a 22 kW onboard charger exist; for them the comparison is a tie. The DC advantage lives exactly where the AC cap sits below 22 kW.
- Plug-in hybrids. Most PHEVs take AC only, with no DC path at all — for them this comparison never starts. Check the car’s specification.
- Low DC acceptance. A few cars cap DC charging low. Their DC figure beats their AC figure, but not the table’s full 22 kW.
So “most” is an acceptance-class statement: most battery-electric cars carry onboard AC chargers rated below 22 kW, and those are the cars DC outruns at equal kilowatts.
The EV-RHDC30K-L in This Comparison
The EV-RHDC30K-L is the DC side of this article: 22 kW DC on its product page, a floor-standing single-connector unit with an LCD, OCPP 1.6J and an IP54 enclosure. On the AC side, EVDANCE’s EV-ACT3204PE is a 22 kW wallbox — the right tool for the tie case and for cars parked for hours. The RHDC30K-L’s listing does not name the DC connector standard fitted, so confirm in writing before ordering that it matches your cars. Both units carry EVDANCE’s 3-year standard warranty (EVDANCE: Shenzhen, founded 2011).
Frequently Asked Questions
Does DC bypass the car’s charger completely?
It bypasses the onboard AC charger — the conversion happens in the station. The car’s battery system still runs the session: it sets the DC acceptance and tapers the rate as the battery fills. DC removes one bottleneck, not the car’s control.
Why not just fit a bigger AC post?
Because the post is not the cap — the car is. A dual-connector AC station offering 22 kW per connector still delivers 11 kW to a car whose onboard charger accepts 11 kW.
What two numbers should I check on my car?
Its AC acceptance and its DC acceptance, both in the specification sheet or manual. If the first is 7.4 or 11 kW and the second 22 kW or more, a 22 kW DC charger roughly doubles or triples what an hour of AC gives you, before taper.
Related Reading
- Are EV Chargers AC or DC?
- How Long Does It Take to Charge an EV at 7 kW, 11 kW and 22 kW?
- Level 1 vs Level 2 vs DC Fast Charging: A Practical Comparison
- How Do DC Fast Chargers Work?
