EV charging speeds explained
More and more EV charging points for electric cars are popping up around the country. At the last count, there were almost 1 million public, home and work chargers across the UK.
But the big question for many EV drivers is: how long does it take to charge an electric car?
Our quick guide to EV charging speeds will help you understand the difference between fast charging, rapid charging and ultra-fast charging. We’ll also look at battery capacity, and other factors that affect charging speeds.
How are EV charging speeds measured?
There’s no one-size-fits all formula to work out the time it takes to charge an electric car. But you can get a rough idea by dividing your battery size by the charger’s output power, then multiplying the answer by 0.9 (which is the average power efficiency for electric cars).
Charge time (hours) = battery size (kWh) ÷ charging power (kW) × 0.9
If that sounds like too much hard work, just enter your figures into Inch Calculator – and they’ll do the maths for you!
A more accurate measure is to look at the time it takes to charge a battery from 20% to 80%, as charging speeds are steadier within this range. (Speeds are faster below 20% and slower above 80%).
The table below gives you the time to charge a mid-market car, with a standard 64kWh battery, from 20% to 80% charge.
| Type of charger | Charger power | Approx. Time to Charge |
| 3-pin domestic plug at home | 2.3kW | 19 hours |
| Standard home EV charger | 7kW | 6 hours |
| Public on-street or workplace charger | 22kW | 2 hours |
| Charger at a hotel or forecourt | 50kW | 1 hour |
| Charger at a supermarket car park or forecourt | 150kW | 20 mins |
| Ultra-rapid charger at a motorway service station | 350kW | 8 mins |
*Simplified for example purposes; data source Inch Calculator
How long does it take to charge an EV?
The time it takes to charge an electric car depends on five key factors:
- The type of EV charger (AC or DC)
- The power of the charger (kW)
- The car’s battery capacity and charging rate (kWh)
- The state of charge (or how full the battery is)
- The weather and battery temperature
Let’s take a look at how each of these affects charging speeds.
AC chargers vs DC chargers
What is an AC charger?
An AC charger is the most common type in the UK. You’ll find them in homes, streets and multi-storey car parks.
They charge your car with AC (alternating current) electricity – the type supplied to homes and businesses by the National Grid.
But electric car batteries can only store DC (direct current) electricity. To get round this, the car’s built-in onboard charger converts the AC power into DC power before sending it to the battery.
What is a DC charger?
DC chargers convert AC to DC power within the unit itself. This means they can bypass the car’s onboard charger to deliver a DC charge directly to the battery.
Charging speeds are much faster, which is why DC chargers are also known as ‘rapid chargers’ and ‘ultra-rapid chargers’. The Tesla Supercharger is a type of DC charger.
You’ll find rapid and ultra-rapid DC chargers across the public network, including at petrol stations and motorway service stations.
Comparing the power of slow chargers, fast chargers and ultra-fast chargers
An EV charger’s power rating is given in kilowatts (kW). This is a measure of the power it can deliver to your car. A charger with a high kW rating will generally charge faster than one with a low kW rating.
You’ll often see AC chargers described as ‘slow chargers’, and DC chargers as rapid charging. But there’s more to it than that.
AC charging speeds
- Slow charging – 1.4kW to 7kW of power.
- A standard three-pin (UK) domestic plug on average delivers 2.3kW.
- A standard EV home charger is 7kW. In some cases, a 7kW home charger can be increased to an 11kW power output during installation, though this depends on the home’s AC supply. This is limited by the grid connection and what power is being used by the house.
- Fast charging – 8kW to 49kW.
- Most standard public street chargers and workplace chargers are 22kW.
- Home EV chargers in large or new build properties with a 3-phase electricity supply can install a 22kW.
DC charging speeds
- Rapid charging – 50kW to 149kW of power (found at forecourts and motorway service stations)
- Ultra-rapid charging – 150kW to 350kW (found at specialised EV-charging forecourts and motorway service stations). Some EV chargers can deliver over 350kW, though these are usually installed for HGVs.
Overview of EV charger speeds
Level 1 charging, level 2 charging and level 3 charging
You might also come across charging speeds described as:
- Level 1 – the same as slow charging; delivers up to 3kW from a domestic 3-pin plug
- Level 2 – the same as fast charging; delivers 7kW to 22kW of power from a standard home charger
- Level 3 – describes all forms of rapid and ultra-rapid DC charging, from 50kW plus
How a car’s battery capacity affects charging speeds
An electric car’s battery capacity is measured in kilowatt hours (kWh). That’s the unit that tells us how much energy is going into the battery from the charger.
A battery with a bigger capacity typically takes longer to charge (though it will generally give you more mileage).
But that isn’t the full picture. The battery’s cell type, construction and cooling system also play a part in the charging speeds that can be achieved – as does the car’s battery management system (BMS).
The battery in an electric car defines how quickly it can be charged. Charging an EV is like filling up your kettle with water, the kettle defines how much water it can hold. When empty, you turn the tap on full to quickly fill the kettle up. As it nears the top, you slow the tap down to make sure the kettle doesn’t overflow. It is the same theory with electric vehicle batteries. They charge quickly when empty and as they fill up, the charge rate needs to slow down to ensure you don’t over charge the battery.
The car manufacturer’s specifications will give you a guide to the charging speeds the EV model can achieve.
What’s the difference between kW and kWh?
Kilowatts (kW)
A kW is the measure of power delivered by an EV charger to an electric car. The lower the kW rating, the slower the charger; the higher the rating, the faster the charging speed.
The power-rating of slower AC chargers range from 1.4kW to 22kW; while faster DC chargers generally range from 50kW to 350kW.
Kilowatt hours (kWh)
A kWh is a unit of power. It tells us how much energy has gone into the car battery from the charger. The battery’s capacity is given in kWh – it’s the equivalent of a petrol tank’s capacity, which is given in litres.
How a battery’s state of charge (SoC) affects charging speeds
State of charge means how full an EV battery is. It plays a big part in the time it takes to charge an electric car.
When a battery has less than 20% charge, it takes less effort to pull charge into the battery. This means the charging speed will be higher.
Charging speeds are steady when the battery charge sits between 20% and 80%, but slow dramatically after 80%.
Why does the charge speed slow past 80% battery capacity?
The physics of a car battery slows the battery speed when it’s charged at 80% or more. The fuller the battery is, the slower it absorbs energy.
It’s a bit like finding a seat in a room full of chairs. If you arrive early, the room is empty and you can quickly find a seat. Once the room fills up, finding an empty chair takes more effort – and more time.
Plus, most car manufacturers’ software deliberately slows the charging speed once 80% is reached. This prevents the battery from overheating and protects its lifespan.
The EV battery charging curve explained
The charging curve is the variation of charging power throughout the charging session. It’s represented as a curve, as it’s not a constant flow of electricity to the battery.
The charts below show the AC and DC charging curves of a typical EV battery. You can see that the speed of charge (power output) starts off slowly when the battery is less than 5% charged.
Generally, the fastest charging happens when the SoC is between 5% and 20%. Speeds then level off until 80%, when they take a rapid dip.
AC charging curve
The reason the AC charging curve is lower on the scale, is because the EVs onboard charger is limited by the power it can receive.
DC charging curve
The charging curve line on the DC is much higher, because the battery can receive more energy, as the EVs onboard charger is bypassed.
How weather and temperature affect charging speed
Ambient and battery temperature both affect how long it takes to charge your car.
Charging at low temperatures can reduce speeds. The cold weather can slow the chemical reactions within the car battery, making it hard for the ions inside to move around.
A car battery usually needs to be at about 40C to 60C for ultra-rapid charging. The car would generally have to heat the battery for it to reach this. Some cars start the heating process when you set your satnav to go to a rapid-charging station.
High temperatures can increase the internal resistance of a battery and slow charging down. But this is only likely to happen in a hot climate when you’ve been driving fast.
Does it cost more to charge an EV quickly?
Charging with a rapid DC charger costs more than with a slower AC charger.
At the time of writing, the cost of charging at a rapid DC charger is 80p per kWh. The cost of using an AC charger at home is determined by the tariff prices you get from your energy supplier.
Specialised EV tariffs, like Intelligent Go by Octopus Energy, offer low off-peak rates that allow EV drivers to charge overnight for less. At the time of writing, off-peak unit rates are available from 7p per kWh; with peak rates at around 26p per kWh.
There are also thousands of free EV charging points around the UK. Zapmap says that of more than 59,000 charging devices on its map, 2,354 were free to use (April 2024).
Most of these free charge points are fast-destination chargers. They’re found in places like restaurants, supermarkets and garden centres, to encourage you to spend time there while you charge for free.
Average charging speed costs
| Slow AC home charger | Rapid DC charger | |
|---|---|---|
| Cost per kWh | £0.07 (off-peak) £0.24 (peak) | £0.79 |
| Cost per mile | £0.02 (off peak) £0.08 (peak) | £0.26 |
| Cost per 200 miles | £4.00 (off peak) £16.00 (peak) | £52.00 |
*Data source: Which?
Frequently Asked Questions
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Charging an EV does take more time than filling up with petrol – although charging speeds are getting faster as technology evolves.
However, EV charging does have its advantages. With a home or work charging point, you just plug in and leave your car to charge. EV charging is also cheaper – and better for the planet than fossil fuel.
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Megawatt charging uses a high-powered charge point designed to rapidly charge large battery electric vehicles, like trucks, buses and even eVTOLs (electric vertical take-off and landing). Only a few manufacturers have designed megawatt charging stations; the industry is still in its infancy.
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EV drivers often make good use of time by charging their car whenever it’s parked, whether that’s at home, work or out and about. It’s an easy way to keep their battery topped up as part of their day-to-day activities – unlike the regular trip to a forecourt that petrol and diesel car drivers need to do.
About the author
Head of Marketing
Kate’s 20+ year’s experience in marketing spans rapidly scaling climate businesses, a global B2C megabrand and various sectors from engineering to motorbikes to professional services consulting.
Driven to use her marketing skills in profit with purpose businesses, she believes Petalite’s technology innovation is a true market disruptor and will help accelerate the world’s transition to a greener economy.