Engine size: why it affects the price of your car insurance

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Insurance price might not be the first thing you think of when you test drive something with a bit of kick, but that bigger engine will have an impact on your premium.

As a general rule of thumb, the bigger your car’s engine is, the more expensive it is to insure.

Let’s take a look at nuts and bolts of car engines, and see why size has an impact on the cost of your insurance.

There are different engine sizes depending on the fuel type

First things first: a car engine consists of some cylinders and a piston. The fuel is stored and burned in the cylinder, which turns the piston – through some neat mechanics, this drives the wheels.

Petrol car engine groups are split according to the volume of petrol you’d find in the cylinders. The groups are: under 1.0-litre, 1.0 to 2.0-litres, 2.0 to 3.0-litres and 3.0-plus. For a sense of scale, expect big performance cars like an Audi A5 to have the biggest 3.0l plus engines, and a family car like a Ford Focus to have a 1.0l engine.

Diesel engines have the same groupings, except you won’t find a car with an engine under 1.0l. A diesel car is usually a little more expensive than the petrol version, so it can be more expensive to insure (we’ll get to why in a second).

Bigger engines tend to be in higher insurance groups

The size of your engine matters because it determines how powerful your car is. A bigger engine means your car will be more powerful, which would put it in a higher insurance group. The higher your insurance group, the more expensive your insurance – most of the time.

You can check your insurance group using our handy car checker (shameless plug, but it is very handy).

That’s not to say cars with small engines can’t be powerful too – turbocharged engines can be smaller, but are packed with a lot more power. A modern 1.0l engine will often be turbocharged.

Because turbocharged engines are more powerful, they’re generally more expensive to insure. Some insurance companies won’t cover you if you’ve fitted a turbo yourself.

More powerful cars mean you’re more likely to make a claim

Your insurance price all comes down to how likely you are to make a claim.

More powerful cars can get up to and maintain fast speeds easier than a car with a smaller engine (no surprises there). To insurers, that need for speed means a more powerful car is more likely to get into an expensive accident, so you’re more likely to make a claim on your insurance.

This higher potential risk of an accident, and a pricey payout from your insurer, pushes the price of your insurance.

More expensive cars are (generally) more expensive to insure, too

Unsurprisingly, more powerful cars tend to be more expensive to buy than ones with smaller engines. The more valuable your car is, the more expensive it will be to insure. More valuable cars are generally in higher insurance groups and will cost your insurer more if it’s ever written off or stolen.

Expensive, powerful cars are also more expensive to repair, especially if there’s fancy technology involved, so that pushes the claim price up, which – you guessed it – raises the price too.

A bigger engine doesn’t always mean more expensive insurance

How big your car’s engine is isn’t the be-all and end-all of your premium. There are other factors that have different weightings when insurers are working out your premium, too, like your age, your driving history, your postcode and your job title.

It’s all about risk profiles. When they work out your premium, insurers put you into categories based on these factors. How likely people who have similar profiles to you are to claim on their insurance affects your price.

For example, a young driver insuring a powerful car will have a more expensive policy than a driver with more experience. If an insurer knows young drivers are more likely to claim in that kind of car, your price will be higher (and young drivers are more likely to claim anyway).

Manufacturers are also adding swanky new features to cars that can reduce your premium, like high-tech alarms, immobilisers, and Autonomous Emergency Braking (AEB for short). These features can lower your car’s insurance group, because they mean it’s less likely to be stolen or get in an accident.

What if my car doesn’t have an engine?

Electric cars don’t have internal combustion engines. They have an electric motor powered by a battery, which is why you have to charge an electric car.

Electric cars are more expensive to insure than cars with engines because of the cost to repair them. Those lithium batteries are very expensive, and there just aren’t as many mechanics who can repair electric vehicles, making claims more expensive.

Hybrids have a mix of electric motor and combustion engine (the clue’s in the name) – because of the motor, they are more expensive to insure than a car with an engine.

Engine size is just one part of choosing the right car for you

Let’s put our car mechanic hat on. What kind of engine size you need depends on the kind of driving you want to do, and there’s a few more factors to keep in mind: fuel economy, performance, and tax, as well as insurance costs.

As a general rule, the smaller the engine, the more efficient it is – but that doesn’t apply all the time. Smaller engines have to work harder on the motorway to keep up speed, but are much more efficient when you’re driving in town.

While cars with smaller engines are generally cheaper to insure, you should keep the other factors used to work out insurance premiums in mind when you’re looking to take a new car home too.

Updated on 30th September 2020

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