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Powerful cars are a limit to success in the area of environmental protection

Destatis, 27 October 2015

In the discussion about manipulated emission values in the car industry, a greater degree of attention has been focussed again on the ecological balance sheet of passenger cars used by households. In recent years, that balance has been influenced by a strong growth in the number of vehicles and total mileage, but it was particularly influenced by the marked increase in the number of powerful, diesel-fuelled cars. As a result of this trend, no further reductions of fuel consumption or CO2 emissions of cars used by households have been achieved since 2010.

Has the potential for lowering fuel consumption been fully exploited?

Diesel consumption of private passenger carsEnlarge picture

In 2013, households had a fuel consumption of 36.6 billion litres (diesel fuel and petrol, excluding automotive LPG); that was 83% of total fuel consumption of all passenger cars registered in Germany. Compared with 2005, fuel consumption slightly dropped by an overall 3.2%. The reductions were achieved in their entirety in the years before 2010. No further reductions have been achieved up until now.

While the total consumption of petrol dropped by close to 20% in the period under review, diesel fuel consumption experienced a strong increase (+57%). Diesel fuel consumption even more than tripled in the class of the most powerful vehicles with more than 100 kW (kilowatts). Fuel consumption in the category of powerful petrol-fuelled cars has increased, too – however, only by 8%.

Despite the fact that the car manufacturers are developing ever smaller and lighter engines (key word: downsizing) and are recording continuing success in optimizing fuel consumption, the question arises why household fuel consumption has not decreased more strongly since 2005, but has even stagnated recently.

Table: Numbers, mileages, fuel consumption and CO2-emissions of household passenger cars

Households drive ever more powerful vehicles

Number of private passenger carsEnlarge picture

In addition to growing numbers of cars – the year 2013 was characterised by an increase of 7.0% compared with 2005 – a significant trend towards more powerful vehicles has been observed in recent years. According to figures from the Federal Motor Transport Authority (KBA), newly registered cars had an average engine performance of 101 kW (137 hp) in 2013. In 2005, the average engine performance still amounted to only 90.7 kW (123 hp), which means that it rose by a good 11% on average for new registrations since then. An exception to this trend was recorded only for the year 2009 in which the scrapping premium was granted. In that year, the average engine performance of newly registered cars was 87 kW, i.e. even below the value for 2005.

There is a variety of reasons that are responsible for increasing engine performance across all vehicle segments: for instance, customers have ever growing demands for safety and comfort features, and for space in the interior of the vehicles. Four-wheel drive, the availability of automatic or dual clutch transmission, and the trend towards large rims and wide tyres contribute to the fact that the vehicles are characterised overall by increasing size, height, weight and aerodynamic drag, and hence need a more powerful engine in order to achieve an adequate performance. As a result of that trend, the share of vehicles with more than 100 kW in all household vehicles amounted to a good 27% in 2013, while in 2005, that share was only just under 15%.

Demographic change, too, exerts an influence in this context. Since the average age of the cars buyers is rising, they prefer to buy comfortable cars above all. This means, for example, that they prefer cars with a higher seat position which allows the driver to gain a better overview of the situation on the road. In particular the SUVs (sport utility vehicles) seem to offer all those advantages in the eyes of the customers. The share of SUVs in all new registrations has sharply risen in recent years: their market share was just under 6% (close to 200,000 new registrations) in 2005, while in 2014, their share even amounted to more than 17% (close to 530,000 vehicles).

Progressing dieselisation of the passenger car fleet

Number of private passenger cars by type of motor fuelEnlarge picture

The number of diesel-fuelled cars grew by a good 48% to 10.5 million cars between 2005 and 2013. Hence, passenger cars with diesel-powered engines reach a share of close to 27% in the total number of vehicles. That increase occurred mainly in the segment of vehicles with an engine power of more than 100 kW, which accounted for almost half (48%) of all diesel-fuelled cars in 2013. In 2005, the share of powerful vehicles in all diesel-fuelled vehicles had amounted to only 19%.

The number of petrol-fuelled vehicles decreased by approximately 3% to 28.5 million from 2005 to 2013. In the segment of petrol-fuelled cars, too, a shift towards more powerful engines was observed. While in 2005, only 14% of all vehicles had more than 100 kW, their share even amounted to close to 20% in 2013.

Total mileages are on the increase

The average number of kilometres driven by household members in their passenger cars decreased by 3.9% in the comparison period. That decrease may be mainly attributable to the fact that a growing number of households has a second car at their disposition, which means that the rides these households take are distributed across a higher number of vehicles.

Despite lower annual mileages, the total mileage grew by 3.6%, which was due to the strong increase in the numbers of vehicles. In fact, kilometres driven with diesel-fuelled vehicles rose by 57% between 2005 and 2013, while kilometres driven with petrol-fuelled vehicles decreased by close to 15%. That decrease was even more pronounced than was the decrease in the number of petrol-fuelled cars. This is probably attributable to the fact that in particular frequent drivers switched from petrol-fuelled cars to diesel-fuelled cars.

Increasingly powerful engines are a limit to further reductions of fuel consumption

Despite increasing numbers of vehicles – in particular increasing numbers of powerful vehicles with a high fuel consumption – and despite increasing mileages, the total fuel consumption of household passenger cars dropped by a slight 3.2% between 2005 and 2013.

Fuel consumption was lowered primarily thanks to reductions in the average fuel consumption of vehicles, which in fact decreased from 7.9 litres/100 kilometres to 7.4 litres/100 kilometres in the period under review. Hence, arithmetically, there was a reduction of fuel consumption by 3,906 million litres. Those reductions were achieved both by technical improvements (e.g. lightweight construction, improvement of fuel injection technologies, installation of automatic start-stop systems) and possibly also by fuel-saving styles of driving. That effect was even more considerable for petrol-fuelled vehicles than it was for diesel-fuelled vehicles.

In addition to that, the shift from petrol-fuelled cars to diesel-fuelled cars has also contributed to significant reductions. Diesel-fuelled cars have a significantly lower average fuel consumption (6.8 litres/100 kilometres) compared with petrol-fuelled cars (7.8 litres/100 kilometres). On balance, a decrease in fuel consumption by 1,108 million litres can be computed from that.

Table: Factors influencing the fuel consumption of households

By contrast to that, the enormous growth in the number of rather powerful vehicles – which are characterised by a markedly higher average fuel consumption – is a significant contributory factor to higher fuel consumption. Hence, according to studies by the CAR Institute at the University of Duisburg-Essen, an SUV consumes up to a quarter more fuel than a comparable hatchback or sedan, due to its larger size, higher aerodynamic drag and higher weight. For both types of fuelling, a significant increase in fuel consumption of 3,785 million litres in total results from stronger engine powers.

If the passenger car fleet of the year 2013 had been characterised by the same structure of engine performances as in 2005, fuel consumption would have been reduced by as much as 13.2% instead of only by 3.2%.

CO2-emissions might have been reduced to a greater extent

CO2 emissions of private passenger carsEnlarge picture

In 2013, passenger cars owned by households emitted 90.1 million tons of CO2, which was only 1.5 million tons or 1.6% less than in the year 2005. Until 2010, total CO2 emissions were successfully reduced, as was also the case with fuel consumption, but since then CO2 emissions have been going up again slightly.

The diesel-driven cars of households emitted an additional 57% of carbon dioxide in 2013 (+12.4 million tonnes) compared with the year 2005. For petrol-fuelled cars, however, CO2 emissions dropped by nearly 20 % (-13.9 million tonnes); that reduction was hence somewhat more pronounced than was the increase in CO2 emissions for diesel-fuelled cars.

If the passenger car fleet of the year 2013 had been characterised by the same structure of engine performances as in the year 2005, another 9.5 million tons of CO2 would have been saved. Hence, CO2 emissions would have been reduced by 12% instead of only 1.6%.

If the trend towards ever more powerful engines continues and is not counteracted by any other influences, such as further progress in reducing fuel consumption, for example, we will witness a marked increase in fuel consumption in the future again and, as a consequence, also of CO2 emissions generated by private passenger cars.

Author: Petra Fehrentz - Federal Statistical Office
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