EV charger load calculator
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| House maximum demand after diversity | 45 A |
| Main fuse | 60 A |
| Charger power | 7.4 kW |
| Charger supply | Single phase |
| Supply voltage | 230 V |
| Line voltage | 400 V |
Needs load management or a DNO check (total 77.2 A on a 60 A fuse)
- Advisory Total with the charger within the main fuse: 77.174 A UK-wide: BS 7671:2018+A4:2026 Section 722; ENA connect and notify guidance. Check with the source
| Result | Value |
|---|---|
| Outcome (indicative) | Needs load management or a DNO check |
| Charger current (no diversity) | 32.2 A |
| Total with the charger | 77.2 A |
| Headroom on the main fuse | -17.2 A |
Show the working
- Charger: 7,400 W ÷ 230 V = 32.2 A (no diversity)
- Total: 45 A + 32.2 A = 77.2 A
- Headroom: 60 A − 77.2 A = -17.2 A
How it works
- Charger current I = P ÷ V (single phase), or P ÷ (√3 × V_L) per phase (three phase), with no diversity
- Total = house maximum demand after diversity + charger current + other planned loads
- Fits when the total is within the main fuse; if it isn't but the house alone is, a load-managed charger or a DNO check is needed; if the house alone is over, ask your DNO
Most network operators ask to be told about a home charger (connect and notify); the installer usually does this.
PME earthing: an outdoor charging point needs the earthing arrangement in Reg 722.411.4.1. The electrician checks this.
Grants and funding schemes are not covered here.
Indicative only: an electrician or your DNO confirms the supply has room.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Supply voltage | 230 V | Our assumption Not yet checked against the source | Our choice: change it to suit your job UK nominal single-phase supply voltage (brief v2 E2). Researcher to cite the statutory source. |
| Line voltage | 400 V | Our assumption Not yet checked against the source | Our choice: change it to suit your job UK nominal three-phase line voltage (brief v2 E2). Researcher to cite the statutory source. |
Regulations and standards
- BS 7671:2018+A4:2026 Section 722 (electric vehicle charging installations)
- BS 7671:2018+A4:2026 Reg 722.411.4.1 (PME earthing for EV charging points)
- ENA guidance: connect and notify for EV chargers and heat pumps
Explained: BS 7671 (the IET Wiring Regulations), The IET On-Site Guide, Approved Document P (electrical safety).
BS 7671 is used across the UK. Network operators' notification rules are set by the Energy Networks Association for Great Britain; Northern Ireland has its own process.