Due to the nature of the vehicle, plug-in hybrids will need to do the test several times under different conditions. The test will start when the car has a fully charged battery and the test will continue until the battery has gone completely flat. This gives a more accurate representation of the economy that plug-in hybrids can expect. These numbers will then be collated and calculated to work out the official emissions and economy figures depending on the car’s electric range. If you are interested in purchasing an electric vehicle, we have a list of the longest range electric cars with their WLTP figures here.