How Many kWhs Does It Take to Charge a Car?

If you’re new to the EV game or just mulling it over, you’ve probably wondered: "How many kilowatt-hours (kWh) does it take to charge a car?"

Spoiler: it’s not a one-size-fits-all answer, but don’t worry, we’re here to break it down.

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Quick Takeaways:

• A full Charge is between 40-100 kWh, depending on battery size.

• Daily Top-Up: 20-50 kWh for a typical 20%-80% charge.

• Cost: £4.50-£10.80 (at 10-24p/kWh UK rates).

• Range: 3-5 miles per kWh.

kWh: The Electric Fuel Tank

First off, a kilowatt-hour (kWh) is basically how we measure the juice in your EV’s battery. Think of it as the electric version of a tank of petrol, but instead of sloshing litres, you’re packing energy.

Battery sizes vary depending on your ride:

• A nippy little Nissan Leaf might rock a 40 kWh battery.

• The Tesla Model 3 Standard Range Plus? That’s 55 kWh of zap.

• Fancy something beefier like the Tesla Model X? You’re looking at 100 kWh or more.

How many kWhs you need depends on the battery size and how much you’ve run it down.

Simple, right?

Full Charge: The Numbers Game

If you’re charging from flat as a pancake to brim-full, it’s straight-up the battery capacity. A 40 kWh Leaf takes 40 kWh, a 75 kWh Tesla Model 3 needs 75 kWh, easy peasy.

Most folks charge from 20% to 80% to keep things ticking over nicely. For that 75 kWh Tesla:

• 80% - 20% = 60% of 75 kWh = 45 kWh.

Boom, that’s your charge sorted.

Efficiency? Not Quite 100%

Now, charging’s not perfect; some energy sneaks off as heat, especially with those speedy chargers.

You might lose 10-15%, so to shove 45 kWh into your battery, your charger could pull 50-52 kWh from the wall. No biggie, just good to know.

How much will it cost?

What’s the Damage? Cost-wise, it’s all about your electricity rate. As of April 2025, the average UK price is hovering around 24p per kWh (cheers, energy market).

So, that 45 kWh charge?

• 45 kWh x £0.24 = £10.80.

Score an off-peak tariff (perfect for overnight charging), and you could drop to 10p per kWh, £4.50 for the same juice. Compare that to a tank of unleaded, and you’re laughing all the way to the bank.

What Affects Your kWh Needs?

• Battery Size: A Bigger battery, more kWhs. Obvs.

• Lead Foot Syndrome: Hammer the accelerator, and you’ll burn through that charge quicker.

• British Weather: Chilly days can sap your battery’s mojo, so you might need a tad more.

• Charger Vibes: Slow chargers (3 kW) sip efficiently; fast ones (50 kW+) guzzle quicker but lose a bit more.

Miles per kWh: The Range Reveal

How far will those kWhs take you? Most EVs clock 3-4 miles per kWh. With 45 kWh:

• 45 kWh x 3.5 miles = 157.5 miles.

Efficient beasts like the Hyundai Ioniq 6 might stretch to 5 miles per kWh, while chunky SUVs could dip below 3. Depends on your wheels!

How to Calculate Your EV charging Requirements

Now that we’ve got a handle on what a kilowatt-hour (kWh) is and what it measures, let’s figure out how many you’ll need to charge your electric vehicle (EV).

It’s pretty simple, just follow these steps:

1. Figure out how far you drive each day (in miles or kilometers, whatever works for you).

2. Check your car’s efficiency rating (you’ll usually find this in the owner’s manual or with a quick online search - it’s listed as kWh per 100 miles or 100 kilometers).

3. Divide your daily distance by that efficiency rating to see how much energy you’re using.

4. Multiply that number by how full you want your battery (like 80% or 100%) to get the total kWh you’ll need.

Here’s an example to make it clear: Let’s say you drive 30 miles a day, and your car uses 20 kWh for every 100 miles:

Step 1: You’re driving 30 miles.

Step 2: Your car’s efficiency is 20 kWh/100 miles.

Step 3: Energy used = (30 ÷ 100) × 20 = 6 kWh (that’s what you’ve drained from the battery).

Step 4:

• Want to charge back up to 80% from empty? 6 kWh × 0.8 = 4.8 kWh.

• Going for a full 100% charge? 6 kWh × 1.0 = 6 kWh.

So, you’re looking at about 4.8 kWh to hit 80% or 6 kWh to top it off at 100% from zero. If your battery isn’t empty when you plug in, just tweak the math based on where you’re starting from.

The Heatable Take

So, how many kWhs are needed to charge a car? Anywhere from 40-100 kWh for a full blast, or 20-50 kWh for a daily top-up, depending on your EV.

It’s cheap, green, and let’s face it, pretty cool. At Heatable, we’re all about making your home (and your ride) run smarter. Plug in, charge up, and hit the road, electric style!

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