What kW Really Means at a Charge Point — and What It Means for Your Time

The single most useful number on a charging map, and often the most misunderstood. Eight minutes here saves hours of confusion at the bay — wherever you charge across the network.

By Steven Day, Plug-n-Go · Reading time: approx. 8 minutes

A kW is a measure of the rate at which electricity flows. Higher kW = faster charging. A 7 kW home wallbox delivers energy 50 times faster than a 3-pin household plug. A 50 kW DC rapid delivers seven times faster than the home wallbox. A 350 kW ultra-rapid delivers seven times faster than that.

But — and this is where almost everyone gets caught — the charger’s kW rating is the maximum it can deliver. The actual rate is the lower of (a) what the charger can deliver, (b) what your car can accept, and (c) what the local electrical grid can provide at that moment.

This post explains what kW you’ll see in the wild — across the UK, Guernsey and Gibraltar — what your car can actually use, how to estimate how long a charging session will take with reasonable accuracy, and the one thing about charging speeds that the marketing brochures rarely tell you.

kW vs kWh — the source of all confusion

Let’s get this out of the way first because it trips up everyone.

A kW (kilowatt) is a measure of power — the rate at which energy is being transferred. Think of it like the flow rate from a tap.

A kWh (kilowatt-hour) is a measure of energy — the total amount of energy transferred over time. Think of it like the volume of water in a bucket.

If you charge at 7 kW for one hour, you put 7 kWh into your battery. If you charge at 50 kW for one hour, you put 50 kWh in. If you charge at 7 kW for two hours, you put 14 kWh in (different rate, different time, same total).

You pay for kWh — energy delivered to your battery. The kW rating tells you how fast that delivery happens.

Your car’s battery capacity is measured in kWh (e.g. a 60 kWh battery, a 75 kWh battery). The charger’s rating is measured in kW (a 7 kW wallbox, a 50 kW rapid, a 150 kW ultra-rapid). Got it? Good. Onwards.

What kW you’ll see at chargers in the wild

Six speeds you’ll routinely encounter on Plug-n-Go and roaming-network chargers in 2026. The mix is essentially the same across the UK, Guernsey and Gibraltar — driven by the same hardware standards and the same site economics — although the highest-power 300+ kW units are concentrated mostly on UK motorway corridors today, where journey patterns justify them.

• 3 kW — A standard household 3-pin plug. Trickle charging, as it sometimes called. And its sometimes used as ‘emergency-only’ or for plug-in hybrids. You wouldn’t habitually charge an EV this way if you can avoid it.

• 7 kW — The most common home wallbox across all three territories. Single-phase domestic supply. Adds about 25 miles of range per hour to a typical EV. Same number on a Gibraltar bay-fitted apartment charger as on a Guernsey driveway wallbox as on a UK home installation.

• 11 kW — Less common in homes in the UK, Gib and Guernsey; but it is standard in much of mainland Europe. Requires a three-phase electrical supply, which most British homes don’t have. Adds about 40 miles per hour.

• 22 kW — The “fast” AC. Common at workplaces, retail destinations and public AC posts on commercial three-phase supply, across all our three territories. Adds about 70 miles per hour. Note: most cars cannot accept 22 kW on AC — see the next section.

• 50 kW — The first speed of DC rapid charging. The default for most older rapid chargers. Adds about 150 miles per hour.

• 100–150 kW — DC rapid, common at modern motorway service areas and at higher-power sites in our networks. Adds 300+ miles per hour at the peak.

• 2500–350 kW — DC ultra-rapid, the current top of the range at hubs designed for the latest EVs. Adds 500+ miles per hour at the peak. Concentrated on motorway corridors today.

What kW your car can accept (the limit nobody mentions)

Your car has its own maximum charging rate — and it’s almost always lower than the charger’s rating. There are two such limits.

The AC limit, set by your car’s on-board AC charger (a piece of hardware fitted by the manufacturer). Typical values: 7 kW, 11 kW, 22 kW. Most modern EVs in our markets are 7 or 11 kW.

The DC limit, set by your car’s battery and electronics. Typical values for cars sold in the last three years: 100 kW (smaller batteries), 150 kW (mainstream), 250–350 kW (premium and performance).

The actual rate at which you charge is the lower of the charger’s rating and your car’s limit.

A practical example: a Renault 5 E-Tech 52 kWh has an AC limit of 11 kW and a DC limit of 100 kW. Plug it into a 22 kW AC charger anywhere on the network: it charges at 11 kW. Plug it into a 350 kW UK ultra-rapid: it charges at 100 kW.

Compare: a Tesla Model Y Standard has an AC limit of 11 kW and a DC limit of around 175 kW (peak). Plug into the same 22 kW AC charger: 11 kW. Plug into the same 350 kW ultra-rapid: 175 kW. Same charger, very different speeds.

The lesson: read your car’s spec sheet. The two numbers (AC max and DC max) tell you what you can actually use.

The maths — how to estimate session time

A back-of-the-envelope formula that works well enough for planning, anywhere on the network:

Session time (hours) = energy needed (kWh) ÷ realistic average rate (kW).

Energy needed: take the percentage of battery you want to add, multiply by the battery capacity. To go from 30% to 80% on a 60 kWh battery: 50% × 60 = 30 kWh.

Realistic average rate: roughly 75% of your car’s maximum DC rate (because the rate falls as the battery fills — see the next section).

So: 30 kWh ÷ (175 kW × 0.75) = 30 ÷ 131 = ~14 minutes for a Tesla Model Y on a 350 kW UK ultra-rapid.

Same calculation for a Renault 5 E-Tech on the same charger: 30 ÷ (100 × 0.75) = 30 ÷ 75 = ~24 minutes.

The maths get less rosy on slower chargers. Renault 5 from 30% to 80% on a 7 kW AC charger is 30 ÷ 7 = ~4.3 hours. Same Tesla Model Y on the same 7kW AC charger: also ~4.3 hours, because both cars are now limited by the charger, not the car.

Why the rate slows down — the charging curve

Watch a DC rapid session and you’ll see something odd: the kW rate starts high, holds for a while, then drops noticeably as the battery fills. By the time you’re at 80%, the rate has often halved. By 95%, it’s a trickle.

This is the charging curve, and it’s not a fault. It’s a deliberate protection of the battery. Pushing high power into a near-full battery damages the cells, so the battery management system slows the rate down to protect them.

Practical implication: aim for 10–80% on rapid charging journeys, not 0–100%. The last 20% takes nearly as long as the first 70%, and you’ve usually made enough range to get to your next stop.

The shape of the curve varies enormously by car. Newer Korean and German EVs (Hyundai Ioniq 5, Kia EV6, Porsche Taycan) hold their peak rate much further into the session than older designs. The “DC max” number you see in a car’s spec sheet is the peak — what matters for journey time is how long the car holds it.

Temperature and state of charge matter too

Two more variables that affect your actual rate at a charger.

Temperature. Lithium-ion batteries charge fastest in a warm temperature window — roughly 25–35°C. Below that, the battery management system slows the rate to protect the cells; below freezing, you might see half the maximum rate. Many EVs now pre-condition the battery (warm it up) when you set a rapid charger as your destination — use that feature. Worth noting: the rate-slowing effect bites harder in a UK winter than a Gibraltar one, but it can affect a cold morning anywhere.

State of charge at the start. Charging from 5% to 50% is faster per kWh than charging from 50% to 80%. The first half of the battery accepts power more eagerly than the second.

This means the same car, on the same charger, can take meaningfully different times to add the same kWh on different days.

So which charger should you use?

Pragmatic guidance, by use case:

For overnight charging at home

7 kW is plenty for almost any driver across the three territories. 11 kW only matters if you have a three-phase supply and a car that can use it. The economic case for upgrading to a faster home wallbox is rarely there — you’ll be plugged in for eight hours overnight either way.

For workplace and destination charging

22 kW AC is often the default at commercial sites. Even if your car can only use 11 kW, you’ll often see dual sockets on 22kW chargers so two cars can both charge at 11kW at the same time. Even so, an etiquette point: always unplug when you’re charged, not when you’re leaving. That way you’ll avoid any overstay charges.

For journey rapid charging — UK

Match the charger to your car. There’s no point queuing for a 350 kW ultra-rapid if your car peaks at 100 kW — you’re paying premium pricing for capacity you can’t use, and slower 50–150 kW units in the same hub will charge you just as fast at lower cost.

For journey rapid charging — Guernsey and Gibraltar

On both, journeys are short, nowhere is more than 25–30 minutes’ drive away. DC rapid is less central to daily life than it is for UK long-distance drivers.

For driving from Gibraltar across the border into Spain

Spanish rapid coverage is improving fast but is still patchier than the UK on inter-city corridors — covered properly in our Roaming Blog 2 (“Gibraltar to Málaga, Gibraltar to Santander”). The kW maths are the same; the planning challenge is finding a compatible CPO at the right interval.

A kW is like both the speed limit on a road (the charger’s power) and your car’s top speed (based on its power). The actual rate you charge at is the lower of the two. A 7 kW AC charger is plenty for overnight charging anywhere on the network. 22 kW is plenty for destination charging. For rapid, match the charger’s kW to what your car can actually take; don’t queue for a 350kW charger when a lesser powered one will work for your vehicle. Aim for 10–80% on rapid stops, and pre-condition the battery in winter. The same physics applies on every Plug-n-Go and roaming-partner charger across our three territories.

The Plug-n-Go take

The Plug-n-Go app shows the charger’s kW rating at every site — across the UK, Guernsey, Gibraltar and the 800,000+ roaming-partner chargers in 60 countries. Pair that with your car’s known AC and DC limits (set them once in your profile, the app remembers them) and you’ll get reliable, accurate session estimates before you set off — not best-case marketing numbers from the charger manufacturer.

Where we have multiple chargers at one site at different speeds, the app shows you which ones are available and what they cost. For most drivers in most situations, the right answer is the slowest charger that gets you to your next stop comfortably — saves money, frees the higher-speed charger for someone who genuinely needs it.

If a session isn’t doing what you expect — running slower than it should, or not starting at all — our driver-support line on +44 (0)330 232 1111 is answered 24/7, by humans, every day of the year. Free to call, and often the fastest route to working out whether it’s the car, the charger or the cold morning that’s slowing things down.

This is the third post in the foundations series. There’s two more to goof fundamentals, then we move to the practical mechanics of using the network.

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