What does WLTP even mean?
WLTP stands for the Worldwide Harmonised Light-Duty Vehicles Test Procedure (yes, they left out a few letters, but WHL-DVTP would have been far too long), and it’s a lab-based test that calculates the fuel economy/electric efficiency and emissions of new cars.
It was developed for Europe to replace the NEDC, or New European Driving Cycle, which had been around since the 1980s and also came up with fuel economy and emissions figures for cars but they were very generous.
So many acronyms. How long has WLTP been around then?
It was introduced in 2017 for cars that were fresh to the market, and from 2018 it became compulsory for all cars that were already on sale to go through the WLTP too.
What’s it even for?
Well, without a legislated efficiency test, a carmaker could just make up the range figure for its electric cars, or the miles per gallon on its ICE cars, and we wouldn’t know any better. Nor would we be able to make a fair comparison with other cars, or apply tax using these figures as a level playing field.
The WLTP is done on a rolling road (sort of like a fancy conveyor belt) in a lab and it's controlled by a computer, so it’s endlessly repeatable in the same conditions. You can control temperature (23ºC in this case), humidity, the exact speed of the car and for how long it runs.
That means it's fair for everyone, too. It gives you a number that’s both consistent and comparable with all the other cars that have gone through the same test, and all the numbers have to be displayed in dealerships on an easily understandable label that’s stuck on the windscreen. It’s where we get range figures for electric cars, and there’s a requirement for PHEVs that we also get a fuel consumption figure for once the battery has run out.
The WLTP was also designed to give us emissions figures that shape taxation – whether you can go into the ULEZ in London for free, what VED bracket your car falls in, these are all based on the official CO2 or range figures as determined by the WLTP.
How do they actually test cars to get WLTP range and mpg?
A car is tested over 30 minutes on a rolling road and will cover just over 14 miles during the procedure. There are four phases of driving that have progressively higher top speeds – up to around 35mph, 48mph, 61mph and 82mph.
These computer controlled phases all have periods of acceleration, deceleration, constant speed and coming to a stop that are intended to better replicate driving on actual roads – in fact in the first slower phase the car spends 50% of the time at a stop to replicate urban traffic jams. The efficiency and range figures we get are an average of those phases.
Cars that go on sale in the EU have an extra element they have to complete – that’s the RDE (real driving emissions) test, which takes cars out on actual roads for a couple of hours over around 50 miles of mixed roads at different speeds.
It doesn’t give a figure that’s published, rather it’s there to check emissions and make sure that carmakers aren’t trying to trick the system with naughty devices or sneaky bits of software.
But why can’t I achieve the WLTP figure on my car?
The problem is that the WLTP process is designed to be both scientific and repeatable, words which aren’t often used to describe a run to the shops that we might do in every day life.
The mileage our cars get is affected by the weather, traffic, our mood, and our preference for blasting the aircon at 16ºC year round because we run hot. You can learn to drive more smoothly and economically, but even the most efficient drivers find it difficult to get too close to the WLTP figure.
When we test new cars we give them a good run to see how close they can get to the official figure and how consistent they are in real world driving across different conditions.
It’s why we place an emphasis on things like heat pumps being fitted as standard, because they make EVs more efficient in colder conditions, and we’re also looking for cars that give you a realistic sense of how much range you’ve got left on the dash readout.
So now you know what we mean when we tell you that a car can do 250 miles of WLTP range, but real world range will be more like 170 to 220 miles of real world driving.
We always put an emphasis on what real world range and efficiency are like when we test new electric cars 
