Opinion: our passion for SUVs threatens to undermine the major gains from electric cars and electrification won't solve the problem

The argument for electrified transport is clear. We need to drastically cut our emissions to limit the impacts of climate change and to protect local air quality. Despite some misleading claims, electric vehicles (EVs) are far more efficient, result in less Co2 emissions overall and will continue to improve in terms of environmental impact as our national grids incorporate more sustainable generation.

But our passion for larger SUV and crossover-type vehicles threatens to undermine the major gains we can get from this transition. This complex debate is happening at a time when policy makers are considering an SUV tax. So what causes SUVs to be so damaging and why won't electrification solve the problem anyway?

In the last decade we have moved towards SUVs and Crossovers as our preferred vehicles. To provide a distinction, Sport Utility Vehicles (SUVs) are typically large vehicles capable of off-road travel that are built on specialised heavy chassis. Despite their off-road capabilities, most are primarily used for normal commuting and have become status symbols. Imagine a Range Rover rolling up a gravel driveway and you have likely pictured its most challenging off-road use.

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Crossovers tend to have similar off-road pretences, but are typically less capable as they are usually simply lifted and styled to appear off-road ready while being based on a car chassis. It is reasonable to say that most of both vehicle classes are chosen for style over function. But this decision comes with serious drawbacks.

SUVs and crossovers are typically heavier, more expensive and more dangerous for pedestrians. They are also less efficient - a lot less efficient. There are many factors that impact how much energy it takes to move a vehicle. Here, we will focus on the three factors that are most different when we compare SUVs and saloon cars: rolling resistance; mass, and; aerodynamics.

Rolling resistance is how much energy is lost as your tyres move across the road surface. Picture the types of tyres used on road bikes compared to mountain bikes. Road bikes use very narrow tyres inflated to high pressures so that the contact between the road and the tyre is as small as possible. This results in a road bike that rolls along with less resistance meaning you have to pedal less to go further.

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Now consider the mountain bike with its large squishy tyres designed to maximise mechanical grip on a soft surface. These tyres deform and flex more. They also have a much larger contact patches with the ground. This requires more energy to move this bike along the road. This is also true for the SUV. We can see the impact of rolling resistance on any type of EV when we look at trim levels. If you opt for the larger wheel options in the higher trims you will usually lose a significant amount of your projected total range.

Mass is another factor that impacts overall efficiency. As you use energy to accelerate to 100kph a heavier vehicle will use more fuel. As you brake to reduce speed more energy is wasted as heat. Even with regenerative braking all the energy cannot be recovered and so with all other factors being equal, heavier vehicles are also less efficient vehicles.

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Finally, we have aerodynamics. The amount of energy required to push a vehicle through the air at a given speed can be considered its aerodynamic drag. Drag exponentially increases with speed, but there are two key points to consider when comparing vehicles. Firstly, there is the drag coefficient. This is typically experimentally derived and is an expression of how easily a body moves through the air. The lower the number, the easier it is to move that object through the air. For context, the Tesla Model 3 has a drag co-efficient of 0.23, while a Range Rover has a drag co-efficient of 0.35.

The other aero factor to consider is the cross-sectional area. In the equation that allows us to calculate how efficiently a car moves through the air, drag co-efficient and cross-sectional area are separate factors, although they are frequently misinterpreted in auto publications.

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When rolling resistance, mass and aerodynamic drag are considered we begin to see why SUVs are a poor choice for personal transport. When we consider traditional petrol and diesel models this results in significantly more Co2 and NOx emissions, often in heavily populated areas that can result in serious health impacts.

Despite petrol and diesel engines becoming much more efficient in the last decade, our increasing preference for thirsty SUVs have essentially wiped out any environmental benefit. Rolling resistance, mass and aerodynamic drag are even more critical when considering the design of an electric SUV. The larger batteries required to achieve suitable range means that we are putting more pressure on already strained supply lines for essential battery materials such as cobalt and lithium. When the entire lifecycle of the vehicle is considered this also results in a greater impact on the environment, although still less than traditional internal combustion SUVs.

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From an economic perspective, manufacturers are encouraged to produce more SUV style vehicles. They result in higher profit margins and are currently extremely popular with consumers. But there is another reason manufacturers like electric SUVs and that is down to design. EVs tend to have a skateboard like chassis with the large battery packs positioned underneath the car. This results in a taller vehicle. It is difficult to get a hatchback style car to look appealing when it is sitting at an increased height, however it suits the aesthetic of crossovers and SUVs.

Electric SUVs are easier to design and are far more profitable, but they are worse for the environment when compared to similarly large electric cars. If they are prioritised in terms of production by manufacturers they could prevent smaller, more efficient and cheaper EV options being brought to market. For those that need them, SUVs are essential tools. But for those that only utilise their considerable towing capacities for the occasional trip to the local golf club, they are a wilful waste of increasingly scarce resources.


The views expressed here are those of the author and do not represent or reflect the views of RTÉ