Boiling a kettle takes longer if it’s full, if the water’s cold or if your plug socket’s already powering the toaster. Home-charging an EV is surprisingly similar.
Your setup, your timing and, yes, even the weather make more of a difference than most people realise.
At home, most people charge their EVs using a 7kW charger, but that doesn’t necessarily mean you’ll see an additional 7kWh in your battery per hour. How long it takes depends on more than just the battery size.
If you’ve ever wondered whether you’ll need to plug in all night or just top up while when you pop home for lunch, read on. This blog explains how long it actually takes to charge an EV.
Estimating charging times based on battery size and EV charger power
Most UK homes have a 7kW (or 7.4kW) single-phase EV charger. That’s a solid standard for overnight charging, but how long does it take to ‘fill’ a battery?
What’s actually happening is that your home sends alternating current (AC) through the charger and into your EV. Your car’s onboard charger converts the AC into direct current (DC), which in turn flows into your battery cells, causing lithium ions to move and store in the battery’s electrodes. This process stores energy chemically, which your EV later converts back into electrical energy to drive the motor.
Charging speed is measured in kilowatts (kW), and battery size in kilowatt-hours (kWh). For example, in an ideal world, a 7kW charger ideally adds exactly 7kWh every hour. However, in real life, you typically see an efficiency of about 85% to 90%, due to small losses in AC/DC conversion and heat.
Here’s a rough formula for charging time:
Charging time (hours) = Battery capacity (kWh) ÷ (Charger power (kW) × Efficiency)
So, let’s say you have an earlier Tesla Model 3 with a 75kWh battery and a standard 7kW charger. In this case, 75 ÷ (7 × 0.9) = 11.9 hours for a full charge from a completely empty battery. But that’s not strictly fair. Most people rarely charge from anywhere near empty. A typical daily commute uses just 5kWh to 10kWh, so topping up takes far less time, and often gives you the flexibility to delay charging until it suits you.
Realistic overnight and daily top-up charging scenarios
Overnight charging is the most realistic approach for most people. In the example mentioned above, we might expect a typical (older) Tesla Model 3 to charge to full in just under 12 hours. That’s perfect for someone getting home from work and heading out early again the next day. Except, of course, you’ll probably only need a few hours of charging, because your car likely won’t be anywhere near ‘empty’.
Plus, energy companies almost always set cheaper rates at night. That means you’ll pay even less for the same amount of electrical usage.
In some cases, things might be different. For example, if you have a large solar setup, consider looking for EV home chargers with solar and battery integration. Getting the right setup to charge during the day may maximise your solar investment and help you save even more money.
It’s fine to use fast chargers occasionally, but try not to rely on them too often. Regular use over time can increase battery wear, so it’s best to stick with home charging for everyday use whenever possible.
The key isn’t chasing a one-size-fits-all solution. It’s about examining your routine and selecting what works best for you. For many EV owners, overnight charging makes sense. But your schedule, vehicle or setup may well be different. At Electrical Innovations, we’re happy to discuss it with you and help you find the approach that works best for you.
Factors that affect charging duration and smart charging tips
So, what does that theory look like in real life? Well, there are a few things to watch out for. Here are several things that affect how long charging to full range actually takes (beyond battery size and charger rating):
- Battery state of charge – charging slows significantly after 80%, so topping up is often quicker than full charges.
- Temperature – cold batteries accept a charge more slowly. Warming your battery before charging helps. (Some EVs have built-in battery warming.)
- Household load – other appliances can reduce available power; smart chargers with load balancing help prevent overload.
- Cable and connector rating – using a lower-rated charging cable limits the charging speed, even if the charger and car are capable of higher speeds.
- Charger efficiency – not all home chargers deliver the same real-world efficiency. Power lost as heat or through voltage drop can affect total charging time.
- Vehicle’s onboard charger – every EV has a built-in AC charger that caps how much power it accepts. Even with a faster wall charger, the car might limit the speed.
- Battery conditioning systems – some EVs slow charging to protect battery health, especially when charging at high or low states of charge.
- Software updates – manufacturers sometimes adjust charging behaviour to improve long-term battery performance, which may alter how charging ramps or tapers.
How Electrical Innovations helps you optimise EV charging
Charging your EV isn’t as complex as you might imagine. With a little bit of planning, it’ll slot into your everyday routine like anything else.
And that’s where Electrical Innovations can help. We offer advice and installation tailored to your needs and usage requirements. No matter your circumstances – even if you haven’t yet committed to an EV – we’ll help you figure out the best and most cost-effective approach.
Give us a call on 01332 498130 or click the button below to book a consultation. We look forward to meeting you and helping you along your EV journey.
