How Much Energy Does an Electric Car Need to Fully Charge?
As electric vehicles (EVs) become more common on our roads, a lot of us are asking the same question: how much energy does it really take to fully charge an electric car battery?
At first glance, the answer might seem simple. If a battery has a capacity of 60kWh, then surely it must take 60kWh to charge it – just like a petrol car with a 50-litre tank takes 50 litres of fuel, right?
Well, not quite. The reality is a bit more nuanced – and understanding the difference can help you become a more informed EV owner or buyer.
It’s Not Just a Bigger Battery
The battery in your electric car isn’t a passive container like a fuel tank. Instead, it’s a complex, high-tech system that manages energy flow, heat, and charging efficiency – all while prioritising battery health.
For this reason, charging an electric car typically requires more energy than the battery’s rated capacity. In most cases, you’ll use about 10 to 15% more than the listed battery size to reach a full charge.
So, if your EV has a:
60kWh battery, it might take 66 to 69kWh to charge from 0–100%.
100kWh battery, it could require 110 to 115kWh to fully top up.
This difference is due to energy losses that occur during the charging process.
Where Does That Extra Energy Go?
So, why do you end up using more electricity than the battery’s actual size?
It comes down to efficiency. When you plug in your EV, energy is used not only to store power in the battery but also to manage:
Heat – Batteries warm up or cool down during charging, especially with fast chargers.
Charging system operation – The car’s software, cooling systems and onboard chargers all consume power.
Battery management – To protect battery life, the car carefully controls how energy is distributed.
All these factors mean charging losses are part and parcel of EV ownership – much like spillage or evaporation in a fuel system (just far more precise and safer).
Does It Matter Which Charger You Use?
Yes – charging efficiency can vary depending on the type of charger:
Slow and fast home chargers (AC charging): Tend to have lower losses, often around 10%.
Rapid and ultra-rapid chargers (DC charging): Can have slightly higher losses, sometimes up to 15%, especially if the battery is near full or the ambient temperature is extreme.
In other words, the faster you charge, the more heat is generated – and the more energy is used to manage it.
Why This Matters for Your Energy Use (and Bills)
If you’re charging at home, it’s useful to factor in this efficiency gap when estimating your electricity usage and costs.
For example, if your home electricity tariff is 30p per kWh and your car’s battery is 70kWh:
You might assume a full charge costs £21 (70 x £0.30),
But with a 12% loss, you’d actually use about 78.4kWh, which costs £23.52.
Over time, especially with frequent charging, this difference adds up.
Takeaway: Don’t Just Look at Battery Size
When you think about how much energy your EV uses, remember:
Battery capacity ≠ exact energy consumed.
Charging losses of 10–15% are completely normal.
The type of charger, temperature, and battery state all play a role.
Ultimately, EVs remain a far more efficient and sustainable option compared to petrol or diesel cars. But a little knowledge goes a long way in helping you get the most out of every kilowatt-hour.
Want to learn more about how EVs fit into a net-zero future? Explore more posts in our Knowledge Exchange – where sustainable living meets real-world practicality.