AC vs DC EV Charging Explained
All home charging is AC. All rapid charging is DC. But the distinction matters less than you might think — because the real bottleneck is your car's on-board charger.
The Core Difference
Your EV's battery stores energy as DC (direct current). The UK mains supply is AC (alternating current). Something has to convert the AC from the grid into DC the battery can store.
- AC charging: The conversion happens inside the vehicle, in a component called the on-board charger (OBC). All home charge points supply AC.
- DC charging: The conversion happens in the charger unit itself (the big box at a rapid charge station). DC is fed directly to the battery, bypassing the OBC — which is why DC charging is faster.
The maximum AC charging speed is limited by your vehicle's on-board charger — not the charge point. A 7.4kW home charger won't charge a car with a 3.7kW OBC any faster than 3.7kW.
On-Board Charger Ratings — Common Vehicles
| Vehicle | OBC Rating | Max Home Charge Speed |
|---|---|---|
| Nissan Leaf (older) | 3.7kW | 3.7kW |
| Nissan Leaf (newer) | 6.6kW | 6.6kW |
| Volkswagen ID.4 | 11kW (3-phase) | 7.4kW single-phase / 11kW 3-phase |
| Tesla Model 3 (RWD) | 11kW (3-phase) | 7.4kW single-phase / 11kW 3-phase |
| BMW i4 | 11kW (3-phase) | 7.4kW single-phase / 11kW 3-phase |
| Renault Zoe | 22kW (3-phase) | 7.4kW single-phase / 22kW 3-phase |
| Hyundai IONIQ 6 | 11kW (3-phase) | 7.4kW single-phase / 11kW 3-phase |
Level 1, 2, and 3
The Level 1/2/3 classification (more common in North America, but widely referenced in the UK) maps to power and location:
| Level | Type | Power | Location |
|---|---|---|---|
| Level 1 | AC | 2.3kW (13A socket) | Home (emergency) |
| Level 2 | AC | 3.7kW–22kW | Home / workplace / destination |
| Level 3 (DC rapid) | DC | 50kW–350kW+ | Public motorway / hub |
For home use, Level 2 (7.4kW single-phase) is the standard — fast enough to fully charge most vehicles overnight, affordable to install, and compatible with every EV on sale in the UK.
Three-Phase Home Charging
Most UK homes have a single-phase supply, which limits home AC charging to 7.4kW. Some properties — typically larger homes or those in rural areas — have a three-phase supply, which allows AC charging at up to 22kW (if the vehicle's OBC supports it).
EcoHarmony supplies three-phase EV chargers and the appropriate PME protection distribution boards for three-phase installations. Browse three-phase chargers →
Check your meter — a three-phase supply typically has a larger main fuse (100A) and three separate MCBs for the main incoming circuits. If unsure, ask your DNO or an electrician.
Frequently Asked Questions
Can I install a DC rapid charger at home?
Practically speaking, no. DC rapid chargers require three-phase industrial power supplies and substantial electrical infrastructure. The equipment costs tens of thousands of pounds. For domestic use, a 7.4kW AC Level 2 charger is the right solution for the vast majority of homeowners.
Why won't my car charge faster than 3.7kW from my 7.4kW charger?
Your vehicle's on-board charger (OBC) is the limiting factor. If your car has a 3.7kW OBC, that's the maximum AC charging rate regardless of what the charge point can supply. Check your vehicle's specifications to confirm its OBC rating.
Is three-phase home charging worth it?
Only if your vehicle supports more than 7.4kW AC charging and you regularly need to charge a large battery quickly. For most UK homeowners, overnight 7.4kW charging is more than adequate.