This is a difficult question to answer as there are a lot of factors that can affect the adoption rate of electric vehicles. However, some estimates suggest that electric cars could make up around 15-20% of new car sales in the UK by 2025. Of course, this is just an estimate and it's possible that the percentage could be higher or lower depending on a number of factors. But it's safe to say that the number of electric cars on the roads is going to continue to increase in the next few years.