WLTP explained: how this standard helps compare consumption figures
The term WLTP has been popping up all over the automotive world since 2017: in car manufacturers’ brochures and websites and in reviews on the Internet and in magazines. But what exactly does WLTP mean? Where does this consumption standard come from and does it give a realistic picture of consumption, emissions and range? We take you through the origins, operation, advantages and limitations of this test procedure.
What is WLTP?
WLTP stands for Worldwide Harmonized Light Vehicle Test Procedure. It is a globally agreed measurement method to determine energy consumption, emissions and range. The standard was developed by the United Nations Economic Commission for Europe (UNECE) to provide uniform figures worldwide. This allows consumers to objectively compare figures, whether it is fuel consumption and CO₂ emissions or range.
The WLTP replaces the NEDC test. NEDC stands for New European Driving Cycle, a testing method that took off in the early 1980s. Whereas NEDC was mostly theoretical and not very dynamic, WLTP is much more in line with modern traffic.
Why was WLTP introduced?
The NEDC standard deviated further and further from reality. Cars changed and traffic became more and more dynamic; the difference between practice and test laboratory became greater and greater. Cars in real traffic turned out to consume more fuel and produce more emissions than the NEDC figures indicated.
The European Union therefore decided that a more representative, universal and rigorous test was needed. The transition from NEDC to WLTP took place in stages. From September 2017, WLTP was mandatory for new models. As of September 2018, WLTP was mandatory for all new cars sold – including existing models. Since then, NEDC values have given way to those of WLTP. Manufacturers, governments, press and consumers now use only WLTP figures as a reference.
How exactly does WLTP work?
The WLTP is designed to approximate real-world driving as closely as possible in the test environment. That means more variation, higher speeds and more dynamic acceleration. The conditions are precisely defined and always the same for all cars tested, so that all results are produced in the same way worldwide and all cars can therefore be compared. Still, it remains a laboratory test and real-world conditions are never the same.
The WLTP consists of several phases
There are four test stages: low, medium, high and extra high. Low tests at low speeds with lots of accelerating and braking. Medium includes more average city and country road driving; high involves higher cruising speeds. Finally, extra high mimics highway use including speeds of 120 km/h.
The resulting overall picture should reflect how motorists drive today. Thus, the WLTP provides a more realistic picture of the fuel consumption and emissions of internal combustion engine cars and the energy consumption and range of electric models.
For whom are WLTP figures important?
The WLTP figures are used by various parties, each with its own purpose. The (Dutch) government links its tax rates to the WLTP values. Think of the BPM,
Car manufacturers are required to communicate their WLTP values. With the WLTP, they must both comply with international regulations and offer consumers comparable information across all models.
Consumers choosing a car naturally look at cost. Fuel/energy consumption is a big part of that. Thanks to WLTP, you know pretty well what to expect, and for electric cars, range is also very important.
Auto journalists and comparison sites put measured values against WLTP values in their field tests to show what the car consumes and performs in practice.
In what areas did NEDC fall short?
Although the NEDC was adequate for decades, the test results were increasingly distant from reality. During the driving cycle, there was little variation in speed. In addition, the maximum speed was too low and the test was relatively short. Also, the test cycle hardly took into account modern systems such as air conditioning and infotainment. Finally, manufacturers were able to influence the test results through conditions. As a result, the differences between NEDC figures and actual consumption became too large. Thanks to the WLTP test cycle, that margin has narrowed – though in a test lab you can only approximate variable real-world conditions.
Are WLTP values more realistic than NEDC?
Yes. The WLTP is better tailored to real-world conditions. The test takes longer and includes varied, including higher, speeds, with more accelerations. In addition, the test also takes into account equipment and options of the car, which is also loaded a bit heavier by default for the test.
For electric cars, the range is also calculated based on this dynamic test cycle. All this makes the WLTP values less favorable than those of the old NEDC – you saw that during the transition phase of WLTP’s introduction – but they are much more realistic.
Is WLTP only for fuel engine cars?
No. The WLTP applies to fuel-engine cars, all types of hybrid and fully electric cars. The difference for electric cars is that range is calculated and determined based on the WLTP test cycle. Energy consumption is measured and determined in kWh/100 km, whereas it is l/100 km for all fuel cars.
For plug-in hybrids (PHEVs), WLTP is actually even more important because the test indicates how much emission occurs on mixed trips, either both electric and fuel. That value determines possible tax breaks in many countries.
Factors that make practice different from the testing laboratory
Of course, weather conditions are essential. Wind, temperature, precipitation all have an influence. Electric cars, for example, lose relatively much range in cold weather because the battery pack then performs less than in warm weather.
Road conditions also play an important role. Smooth asphalt, cobblestone streets, height differences and slopes are not fully simulated even in the WLTP test. In practice, sometimes you drive mostly short trips in the city, or just a lot of highway driving. On each route, energy/fuel consumption is different.
On loading and driving style, you usually have your own influence. If you drive with four people and/or a lot of luggage, your car has more mass to move than in the WLTP test. So that increases consumption. And hard acceleration, high speed and poor anticipation also increase consumption.
Therefore, WLTP values are guide values. They are the starting point for comparison, but not a guarantee of exact real-world consumption.
WLTP and electric driving
For electric cars, the WLTP is especially important for range – many people are anxious about being stranded with a dead battery. The WLTP range gives a good indication for moderate conditions, but again, practice can vary, especially in winter.
The WLTP is primarily an important basis for comparing models. One EV achieves 400 kilometers in the WLTP test, the other 550. In practice, the ratios are probably the same, although the number of kilometers per trip depends on conditions.
WLTP best method of comparison
Despite its limitations, the WLTP is now the most realistic and fair way to compare cars. The test is rigorous, comprehensive and globally harmonized. This makes it possible to compare gasoline cars, hybrids and fully electric cars based on objective consumption standards.
