If you are looking for a new car, you will naturally want to compare its fuel (or electricity) consumption to alternative models. Even cars within the same range can have different figures, based on the engine, gearbox and even the size of wheels fitted.
A car which uses more energy won’t just be more expensive to run day-to-day, it will also cost more in road tax. Company car drivers have to pay more to the Inland Revenue for ‘gas guzzlers’ too.
To allow us to compare the energy consumption of cars on a ‘level playing field’ basis, all new cars sold in the UK have to be tested using the same method. This is defined by EU law and is called the Worldwide Harmonised Light Vehicle Test Procedure – or WLTP for short. You will see these letters mentioned in brochures, on websites and on the official documents you’ll see on cars in Eden’s showrooms.
To make sure the conditions are fair, the tests are done under laboratory conditions. In addition to measuring fuel consumption, they also register the CO2 and other pollutant emissions from internal combustion engines. Electric cars have their range and energy consumption calculated.
The WLTP regime replaced the previous tests – called NEDC - which were designed in the 1980s and had become discredited as they were felt to be unrelated to real world conditions.
The new WLTP cycle was developed using real-driving data from around the world, but the actual test is done on a rolling road to ensure everything is equal from one test to the next.
The equipment used looks similar to some of the machines you might see in Eden’s MoT workshops. But unlike our workshops, the temperature is closely monitored in every test to ensure every detail is the same for every car.
The evaluation is then divided into four parts with the car driving at simulated average speeds. The low section is at 35mph, a medium at 47mph, high at 60mph and extra high at 81mph. Rather than being at a constant speed, each section includes a variety of stops, acceleration, and braking phases – just as would happen in the real world.
To make sure the best and worst example of each car are tested, every powertrain configuration is put through the cycle and the published WLTP figure will show the numbers for the most and least economical version.
The WLTP figures you see in the brochures and official documents are possible to achieve, but only in certain conditions. Electric car drivers will notice that their range figures improve in milder weather, for example.
But it is likely that you will find the official figures are on the optimistic side, and you might find that you use more fuel or energy than is suggested in the WLTP results. The experts at Eden will be able to give you an idea of what you can realistically expect in your ‘real world’ based on your driving patterns and needs.
Yes, electric and hybrid cars go though the same tests, except there is obviously no need to measure the exhaust emissions of a 100% electric car! However, you will see a WLTP figure which shows how far an EV will go before it needs recharging – both for pure electric and PHEV vehicles.