Installation & Power
Single-Phase vs Three-Phase EV Charging: Power, Cost and Which to Choose
Single-phase or three-phase EV charger? Power by supply and amperage, what the car can accept, installation cost and phase balance in one buyer’s guide.
- Prepared by
- VULTAE Engineering Team
- Published
- Reading time
- 3 min
- Sources
- 3 references
Key takeaways
- 1Power = voltage × current (× 1.73 for three phase). On a 230 V single-phase supply, 32 A gives 7.4 kW. On a 400 V three-phase supply, 16 A per phase gives 11 kW and 32 A per phase gives 22 kW.
- 2The car decides how much it can take. Many cars accept 7.4 kW single-phase or 11 kW three-phase on AC; fewer accept 22 kW. A 22 kW charger does not charge an 11 kW car faster.
- 3Three-phase wiring costs a little more but delivers 3× the power at the same current per phase. If the building has three-phase supply, it is usually the better choice for workplaces and shared sites.
- 4In North America, homes have 240 V split-phase supply (about 11.5 kW at 48 A); three-phase 208/480 V is for commercial buildings and DC chargers.
Contents
Short answer: single-phase charging gives up to 7.4 kW (230 V, 32 A) in most of the world. Three-phase gives 11 kW at 16 A per phase or 22 kW at 32 A per phase. The car sets the limit — many cars take 11 kW at most — so match the charger to the car and to the building’s supply, not to the largest number on the brochure.
Power by supply
| Supply | Current | Power |
|---|---|---|
| 230 V single phase | 16 A | 3.7 kW |
| 230 V single phase | 32 A | 7.4 kW |
| 400 V three phase | 16 A per phase | 11 kW |
| 400 V three phase | 32 A per phase | 22 kW |
| 240 V split phase (North America) | 32 A | 7.7 kW |
| 240 V split phase (North America) | 40 A | 9.6 kW |
| 240 V split phase (North America) | 48 A | 11.5 kW |
The formulas: single phase P = V × I; three phase P = 1.73 × V(line-to-line) × I.
What the car accepts
The charger offers power; the car’s onboard charger chooses how much to take.
| Vehicle onboard AC charger | What a 22 kW charger delivers |
|---|---|
| 3.7 kW (some older or small cars) | 3.7 kW |
| 7.4 kW single phase | 7.4 kW |
| 11 kW three phase | 11 kW |
| 22 kW three phase (some models) | 22 kW |
So a 22 kW charger is not faster for most cars today, but it is useful at shared sites with mixed vehicles, and it will suit the next generation of cars. For faster charging than 22 kW you need DC — see AC vs DC chargers for business.
Which to choose
| Situation | Choice |
|---|---|
| Home with single-phase supply | Single-phase 7.4 kW |
| Home with three-phase supply | 11 kW three-phase, if the car accepts it and the supply has capacity |
| Workplace, hotel, retail | 11 kW three-phase, or 22 kW where cars can use it |
| Apartment building | Several single or three-phase chargers with load management |
| Fleet depot | Three-phase 11–22 kW AC for overnight; DC for fast turnaround |
| North America, home | 240 V, 32–48 A |
| North America, commercial | 208/240 V AC (commercial buildings) or DC fast chargers on 480 V |
Cost differences
A three-phase charger needs a five-core cable (three phases, neutral, earth) and a three-pole breaker. The cable is more expensive per metre, but each conductor carries only a third of the power, so the cost per kW is usually lower. For 22 kW the alternative on single phase would be impossible. The bigger cost question is the supply upgrade: if the building’s main fuse cannot take the extra load, the upgrade costs more than the charger. See grid power for DC sites for the same logic at higher power.
Balance and neutral
Several single-phase chargers on one board should be spread across the three phases. Otherwise one phase overloads while the others idle. Three-phase chargers draw equal current on all phases, so balance is automatic. The neutral carries almost no current in a balanced three-phase load.
Single-phase charger on a three-phase supply
It is fine. Use one phase for each charger and rotate. Some chargers can also switch phases automatically to use solar surplus or to balance load.
What VULTAE offers
Our wall-mounted AC chargers are available for single-phase and three-phase supplies from 3.7 kW to 22 kW, and our North American AC chargers run at 32, 40 and 48 A on 208–240 V. Choose the right version in the product pages and use the charging calculator to see how long a charge will take at each power. For the cable and breaker, see wire size tables.
Questions buyers ask
- How many kW is a single-phase EV charger?
- On a 230 V supply: 3.7 kW at 16 A, 7.4 kW at 32 A. In North America, on 240 V: 7.7 kW at 32 A, 9.6 kW at 40 A and 11.5 kW at 48 A.
- Is 22 kW charging worth it?
- Only if your cars can accept it. Many popular electric cars have 11 kW AC onboard chargers, and some accept only 7.4 kW. A 22 kW charger helps fleets with mixed vehicles and some vans and premium models. Check the cars first.
- Can I run a three-phase charger on a single-phase supply?
- It will work as a single-phase charger at the single-phase limit, if the charger supports it. The unused phases do nothing. Check the charger’s data sheet.
- Do I need to balance phases?
- On sites with several single-phase chargers, spread them over the three phases so the load is balanced. Load management can help. Three-phase chargers load the phases evenly.
References
- [1]IEC 61851-1:2017 — general requirements. International Electrotechnical Commission.
- [2]IEC 60364-7-722:2018 — supplies for electric vehicles. International Electrotechnical Commission.
- [3]NFPA 70 (National Electrical Code). NFPA.
