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5 things you need to check before buying a new electric car

Tristan Young

03 Dec 2020


At the risk of stating the obvious, electric cars are not like cars with a petrol or diesel engine. Therefore, buying a fully electric car is similarly different.

We’re not talking about the purchase process; we’re talking about what you need to know, and check, before you choose which electric vehicle is best for you.

In a conventional petrol or diesel car, nobody worries about the size of the fuel tank or the speed with which you can fill up at the pumps because we know there are plenty of filling stations and almost every liquid-fuelled car on sale will go at least 300 miles. If we want to go further, it takes just five minutes to top up and go again.

In an electric car there are differences such as varying battery sizes (even within the same model) and different cars will take on electricity at different rates. With the Government’s commitment to banning new petrol and diesel cars from 2030 we’ll all have to switch to electric eventually, so here’s our list of the five things you need to know before buying your first new fully-electric car.

1. Battery size

Battery size is one of the factors that impacts range. Everything else being equal, the bigger the battery the better the range. Battery size or capacity is measured in kilowatt hours (kWh).

However, some car manufacturers supply the battery size as the total amount of electricity it can hold and others list the useable capacity. The latter being smaller.

Because car batteries are designed to operate within certain parameters to help their longevity, the car’s software won’t let them ever run completely out of charge as this would damage the battery. This is why the useable capacity is a better figure to know as it will allow you to calculate your charging costs and the car’s range.

For example, you can buy a Volkswagen ID3 with either a 62kWh or an 82kWh battery, but the usable capacity of each is actually 58kWh and 77kWh respectively – which is how VW labels the cars.

2. Range

While almost nobody worries about how far their petrol or diesel car will go on a tank of fuel. But because, historically, EVs have had significantly shorter ranges buyers have tuned in to this factor. The term ‘range anxiety’ is often used, but this will become less of a factor as more, longer-range EVs come to market.

Car makers supply official range figures as they would supply official mpg figures for a petrol or diesel car. And like these figures, they are just a guide to the car’s range and should be treated with caution. Factors such as driving style, speed and the temperature can all impact a car’s range.

3. Efficiency

An electric car’s equivalent of miles per gallon is typically stated as miles per kilowatt hour (m/kWh). In other words, how far you can go on 1kWh.

Sticking with the all-electric VW ID3 as an example, the 58kWh battery version, in Pro trim, has an official figure of 4.2m/kWh (range 260 miles). The bigger battery 77kWh version in Pro S trim is capable of 4.1m/kWh (range 341 miles).

This slight difference neatly illustrates that while you need a bigger battery to go further, the additional weight can impact efficiency.

While most car makers use miles per kWh, some may use a different figure. Nissan, for instance, quotes watt hours per kilometre. For the 62kWh Leaf, Nissan quotes an official efficiency figure of 0.185Wh/km. If you get on the calculator that converts to 3.4m/kWh.

Knowing the efficiency figure and the cost of your electricity will allow you to compare the fuel cost per mile.

4. Charge rate

Unlike a petrol or diesel car where the speed with which you can add fuel to your car is governed by how hard you squeeze the pump handle, the speed with which electricity flows into your EV is governed by a host of factors.

The two main points are how fast the charge point will deliver electricity and how fast your car will accept that electricity.

While you can’t adjust the delivery side of charging – other than picking a faster charge point – you can help yourself by picking a car that allows a higher rate of charge.

The Porsche Taycan has one of the fastest maximum charge speeds at 262kW. That means that if you can find a charge point delivering electricity at this rate, you can charge from 10% to 80% full (the equivalent of adding 164miles range) in 20 minutes.

However, an MG 5 EV with a maximum charge speed of 50kW will take 48 minutes to go from 10-80% and only add 122 miles of range – even if the plug-in point is capable of delivering electricity faster.

It’s important to know this maximum charge rate for a car because as ultra-fast charge points become increasingly common with delivery speeds above 100kW it will be the car that is the limiting factor.

5. Charge times

The time it takes to charge will be more important to some drivers than others. If you don’t do long distances and your car is mostly parked at home and plugged in to your wall-box, then several hours to charge isn’t an issue. However, if you do even the occasional longer journey that is beyond your car’s range then charge times will be important and could be the difference between adding 20mins for recharging on top of a two-hour journey versus spending an hour on top of a two-hour trip.

Charge time, like charging speed, is governed by a host of factors including the speed of the charge point, the car’s maximum charge rate and the size of the battery.

However, the easiest comparison figures to look up or ask the dealer is for is the empty to full figure from a (typical) 7kWh home wall-box. In the case of some cars with larger batteries this could be quite a while. For instance, the Jaguar iPace with a useable battery size of 84.7kWh would take just over 12 hours. It’s worth remembering the car will probably be parked that long at your house overnight and that it probably won’t be charging from fully empty. However, this figure is a useful comparison figure.

And finally

While charging an electric car is at a basic level as easy as filling a car with petrol or diesel, having the knowledge about a electric car’s efficiency and the factors that contribute to charge times and range before you buy will help you make a more informed decision about which EV is best for you when you make the switch away from liquid fuels.

Tristan Young

03 Dec 2020