You’ve spotted EV charging cables listed at 16 amps and 32 amps, and you’re wondering whether the ampere rating matters or whether it’s a spec that only electricians worry about. It matters. The amps rating sets the current ceiling for charging, which sets the power ceiling, which sets the speed. For most UK home charging situations, 32A is the right cable. But there are genuine, legitimate reasons a 16A cable exists, and they’re worth understanding.
What amps means in EV charging
Amperes (amps, A) measure the flow rate of electrical current. In EV charging, the current your cable carries, multiplied by the voltage, determines the power in kilowatts:
Power (kW) = Current (A) × Voltage (V) ÷ 1,000
On a standard UK single-phase supply at 230V: - 16A × 230V = 3,680W = 3.7kW - 32A × 230V = 7,360W = 7.4kW
The cable’s ampere rating sets the maximum current it can safely carry continuously. A 32A cable can carry any current up to 32A safely. A 16A cable cannot safely carry 32A. It is a fire risk if asked to do so. Match the cable to the circuit, or go higher.
For a deeper explanation of how amps, volts, and kilowatts interact in EV charging, our guide on amps explained in more detail covers the full picture.
The amps-to-kilowatts conversion: a quick reference table
- Table with cols: Current rating | Phase | Voltage | Power output | Typical application. Rows: 16A | Single-phase | 230V | 3.7kW | Blue Commando socket, older 16A wallboxes; 32A | Single-phase | 230V | 7.4kW | Standard UK home wallbox (most common); 16A | Three-phase | 400V | 11kW | 11kW public AC post (cable at 16A limit); 32A | Three-phase | 400V | 22kW | 22kW destination charger. Highlight 32A single-phase row as most common UK home setup.
The key point from the table: 32A single-phase delivers exactly double the charging speed of 16A single-phase. At a 32A home wallbox, a 32A cable charges twice as fast as a 16A cable. This is the meaningful difference for most home charging situations.
Why 16A cables exist: the legitimate use cases
A 16A cable is not a cost-cut compromise. It is the correct cable for certain charging sources. The most important is the blue Commando socket.
IEC 60309 (the international standard for industrial plugs and sockets, which specifies what most people call “Commando” sockets in the UK) defines two relevant AC variants:
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Blue 16A single-phase Commando socket: Common at caravan sites, marinas, outdoor markets, and some workshop facilities. Rated at 16A. A 32A Commando plug physically won’t fit a 16A socket. The pin configuration and body size differ by design. For this source, a Type 2 to 16A blue Commando cable is the only option.
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Red 32A Commando socket (single-phase or three-phase): Found in workshops, industrial units, some commercial properties. Delivers higher power. Requires a correspondingly rated cable.
For anyone charging from a blue Commando socket (at a caravan site, a marina berth, or a site compound), you need a 16A-rated cable. Our Type 2 to Commando cable guide covers both variants in detail.
Other situations where 16A may be the available option: - Older home wallboxes installed on 16A circuits (less common now but not rare in installations pre-2020) - Temporary site power at outdoor events or construction sites - Some public car park chargers designed for slower, longer-stay charging
Cable thickness, weight, and heat at 16A vs 32A
Higher current cables must be physically larger. This is not a marketing decision, but a consequence of how heat is generated in a conductor.
The power dissipated as heat in a conductor is proportional to the square of the current (P = I²R, where R is the resistance of the conductor). Double the current and you quadruple the heat generated. To keep the cable at a safe operating temperature under load, the conductor must have a larger cross-sectional area, reducing resistance per metre.
In practice: - A 16A Type 2 cable typically uses 4mm² copper conductors - A 32A Type 2 cable typically uses 6mm² copper conductors
This sizing is not arbitrary: it follows conductor sizing requirements embedded in BS 7671:2018+A2:2022 (IET Wiring Regulations), Section 722, which governs EV charging installations.
- Side-by-side cross-section view of two cables. Left: 16A cable with 4mm² copper conductor, insulation, sheath, outer diameter ~18mm. Right: 32A cable with 6mm² copper conductor (visibly larger), insulation, sheath, outer diameter ~22mm. Label conductor sizes (4mm² and 6mm²). Add note: Larger cross-section = lower resistance per metre = less heat at higher current = safe to use at 32A.
The resulting weight difference for a 7m cable is roughly 400-600g. A 32A cable is heavier than a 16A cable of the same length, but neither is difficult to handle. In our own experience handling and testing cables, the gauge difference is noticeable as stiffness as much as weight: a 32A cable has a slightly larger bend radius and is marginally less flexible than a 16A cable in cold conditions.
Commando socket compatibility: blue 16A vs red 32A
The Commando socket family under IEC 60309 uses different physical bodies for different current ratings, specifically to prevent connection of equipment to a supply it cannot handle:
- Blue 16A single-phase: Earth pin at the 6 o’clock position. Small body (approx 50mm diameter). Accepts 16A single-phase plugs only.
- Red 32A (single or three-phase): Larger body (approx 70mm diameter). Earth pin position differs. Will not accept a 16A plug.
This physical incompatibility is a safety feature, not an inconvenience. It ensures you cannot accidentally plug a 16A-rated device into a 32A supply without an appropriately rated intermediate cable.
For EV charging from Commando sockets, you therefore need the correct cable for your socket type. The two are not interchangeable by plugging: a 32A cable’s Commando plug will not physically enter a 16A socket.
Should you buy a 16A or 32A cable?
For standard UK home wallbox charging on a 32A circuit: buy a 32A cable. It delivers 7.4kW, double the speed of a 16A cable on the same supply. Every modern UK home wallbox installation operates on a 32A dedicated circuit (as specified under BS 7671:2018+A2:2022, Section 722). Buying a 16A cable for this situation unnecessarily limits your charging speed.
For a 16A Commando socket (caravan site, marina, outdoor site): buy a 16A compatible cable. You have no choice: the socket physically dictates the connector, and the circuit dictates the current. A 32A-rated cable with a 16A Commando plug will still deliver only 3.7kW (the 16A circuit limits the current), but at least it is electrically safe.
Can you use a 32A cable on a 16A circuit? Yes, safely. A cable rated at 32A can operate at any current up to its limit. Plugged into a 16A circuit, the circuit protection limits current to 16A and the cable operates at 3.7kW without complaint. The rule is: cable rating ≥ circuit rating. Never the reverse.
For the broader decision on power class, including how amps and phase interact, our 7kW vs 22kW power class guide covers the full picture.
Frequently asked questions
Is a 32A cable always better than a 16A cable?
At a 32A wallbox, yes: it delivers 7.4kW vs 3.7kW. But at a 16A source (blue Commando, older 16A circuit), a 32A cable delivers the same 3.7kW as a 16A cable. The source limits the speed; the cable just needs to match or exceed the circuit rating.
Can I use a 32A cable on a 16A charger?
Yes, safely. A 32A cable is rated for up to 32A and can operate at any current below that without issue. The 16A circuit protection limits current to 16A; the cable handles it normally.
Is a 16A EV cable safe?
Yes, for 16A circuits. A 16A cable is designed, tested, and certified for 16A continuous operation. The risk arises only if a 16A cable is asked to carry more than 16A, which would only happen if incorrectly connected to a 32A circuit without appropriate protection.
What is a blue Commando socket and which cable does it need?
A blue Commando socket is an IEC 60309 16A single-phase industrial socket commonly found at caravan sites, marinas, and outdoor work sites. It physically accepts only 16A plugs. For EV charging from a blue Commando socket, you need a Type 2 to blue 16A Commando cable.
Why is a 32A cable thicker than a 16A cable?
Because higher current generates more heat (proportional to I²). Larger copper conductor cross-sections (6mm² vs 4mm²) reduce resistance per metre, keeping the cable cool under load. This conductor sizing is specified in BS 7671:2018+A2:2022, Section 722.