The Q5 is available as a plug-in hybrid. If you can charge a car at home, it can run for up to 26 miles under electric power alone. This is great if most of your journeys are within this range - it'll run around silently without using any fuel. Then you have the support of a petrol engine if required for a longer journey. If you rarely charge it or mainly cover longer journeys, there aren't many advantages to a plug-in hybrid over a standard petrol car.