Electric vehicle (EV) charging points are becoming more widespread across the UK, with nearly 1 million public, home, and work chargers available as of the latest count.
For many EV drivers, one of the most pressing questions is: How long does it take to charge an electric car?
This quick guide to EV charging speeds will explain the differences between fast charging, rapid charging, and ultra-fast charging. We will also explore battery capacity and other factors that influence charging times.
How are EV charging speeds measured?
There isn’t a universal formula for calculating the time required to charge an electric vehicle, but you can get a general estimate by dividing the battery size by the charger’s output power, and then multiplying the result by 0.9 (which is the average power efficiency for electric cars).
Charge time (hours) = battery size (kWh) ÷ charging power (kW) × 0.9
If you prefer not to do the math yourself, you can use Inch Calculator to automatically calculate the time for you.
For more accuracy, consider the time it takes to charge the battery from 20% to 80%. Charging speeds are generally steadier in this range, while charging is faster below 20% and slower after 80%.
The table below shows the approximate times needed to charge a mid-market car with a 64kWh battery from 20% to 80%:
| 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 minutes |
| Ultra-rapid charger at a motorway service station | 350kW | 8 minutes |
How long does it take to charge an EV?
The time it takes to charge an electric car is determined by five key factors:
- The type of EV charger (AC or DC)
- The charger’s power (kW)
- The car’s battery capacity and charging rate (kWh)
- The state of charge (SoC), or how full the battery is
- The weather and battery temperature
Let’s explore how each factor affects charging speeds.
AC chargers vs DC chargers
What is an AC charger?
An AC charger is the most common type in the UK, found in homes, streets, and multi-storey car parks. It delivers AC (alternating current) electricity the type supplied by the National Grid to homes and businesses.
However, electric car batteries can only store DC (direct current) electricity, so the car’s onboard charger converts AC into DC before sending it to the battery.
What is a DC charger?
DC chargers convert AC into DC power within the unit itself, allowing them to bypass the car’s onboard charger and deliver a DC charge directly to the battery.
This results in much faster charging speeds, which is why DC chargers are also called “rapid chargers” and “ultra-rapid chargers.” Tesla Superchargers are an example of DC chargers.
Rapid and ultra-rapid DC chargers can be found across public networks, including at petrol stations and motorway service stations.
Comparing slow, fast, and ultra-fast chargers
An EV charger’s power rating, measured in kilowatts (kW), indicates the power it can deliver to your car. A higher kW rating typically means a faster charging speed.
AC chargers are often referred to as “slow chargers,” while DC chargers are known for rapid charging. However, the charging speeds are more nuanced than just these labels.
AC charging speeds:
- Slow charging: 1.4kW to 7kW
- A standard three-pin (UK) domestic plug typically delivers 2.3kW.
- A standard home EV charger is 7kW. Some home chargers can deliver up to 11kW, but this depends on the home’s AC supply and its grid connection.
- Fast charging: 8kW to 49kW
- Most public street chargers and workplace chargers offer 22kW.
- Homes with a 3-phase electricity supply may install 22kW home EV chargers.
DC charging speeds:
- Rapid charging: 50kW to 149kW (commonly found at forecourts and motorway service stations)
- Ultra-rapid charging: 150kW to 350kW (found at specialized EV-charging forecourts and motorway service stations). Some EV chargers can provide over 350kW, typically for HGVs.
You might also encounter these terms for charging speeds:
- Level 1: Equivalent to slow charging; delivers up to 3kW from a domestic 3-pin plug
- Level 2: Equivalent to fast charging; delivers 7kW to 22kW from a standard home charger
- Level 3: Includes all forms of rapid and ultra-rapid DC charging, from 50kW and beyond
How a car’s battery capacity affects charging speeds
Battery capacity is measured in kilowatt-hours (kWh), which indicates how much energy can be stored in the battery. A larger capacity generally means a longer charging time (but it also gives more range).
However, the charging time isn’t solely determined by capacity. The battery’s cell type, design, cooling system, and the car’s battery management system (BMS) also influence charging speeds.
An EV’s battery functions similarly to filling a kettle with water: when the battery is empty, it charges quickly. As it fills up, the charging rate slows to prevent overcharging.
The vehicle’s specifications typically indicate the maximum achievable charging speeds for the model.
What’s the difference between kW and kWh?
Kilowatts (kW):
A kW measures the power delivered by an EV charger to the vehicle. Lower kW ratings correspond to slower charging speeds, while higher ratings result in faster charging.
Kilowatt-hours (kWh):
A kWh is a unit of energy, indicating how much energy is delivered to the battery. The car’s battery capacity is given in kWh, which is comparable to the capacity of a petrol tank measured in litres.
How a battery’s state of charge (SoC) affects charging speeds
The state of charge (SoC) indicates how full the battery is, and it significantly affects charging times.
When the battery is less than 20% full, it is easier to charge, so the charging speed is faster. From 20% to 80%, charging speeds are relatively steady. However, after 80%, the charging process slows dramatically.
Why does the charge speed slow past 80% battery capacity?
As the battery fills up, it becomes harder for it to absorb energy. The charging rate slows down to avoid overcharging, just like how a full room takes longer to find an empty seat.
Many manufacturers also limit charging speeds after 80% to protect the battery from overheating and to extend its lifespan.
The EV battery charging curve explained
The charging curve refers to the variation in charging power throughout the session. It shows that charging speed is faster when the battery is between 5% and 20% full, and then gradually slows after reaching 80%.
- AC charging curve: The lower power rating of AC chargers limits the speed.
- DC charging curve: The higher power rating of DC chargers results in a steeper curve, providing faster charging.
How weather and temperature affect charging speed
Ambient and battery temperatures both influence charging times.
Cold weather can reduce charging speeds because low temperatures slow the chemical reactions in the battery.
Generally, a car battery needs to be between 40°C and 60°C for ultra-rapid charging, and many EVs automatically heat the battery when heading to a rapid-charging station.
Hot temperatures can increase the battery’s internal resistance, slowing the charging process. This usually occurs in hot climates or after high-speed driving.
Does it cost more to charge an EV quickly?
Charging with a rapid DC charger is more expensive than using a slower AC charger.
At the time of writing, the cost of charging at a rapid DC charger is 80p per kWh, whereas AC home charging costs depend on your energy supplier’s tariff.
Some specialized EV tariffs, like Intelligent Go by Octopus Energy, offer lower off-peak rates, allowing drivers to charge overnight at a cheaper price. At the time of writing, off-peak rates start at 7p per kWh, with peak rates around 26p per kWh.
There are also thousands of free EV charging points across the UK. According to Zapmap, 2,354 of the over 59,000 charging devices in the UK were free to use in April 2024.
These free points are mostly fast-destination chargers found in locations like restaurants, supermarkets, and garden centres, encouraging customers to stay while their cars charge.