The Telegraph points out that CAP didn't factor in the 5,000-pound incentive from the British government for new plug-in vehicles, nor did they calculate the value of free parking and exclusion from London's congestion charge. The publication also notes that Tesla Model S and Nissan Leaf are in their first-generation incarnation, which tends to make people wary about buying them on the used-vehicle market.
That said, there has long been skepticism in the UK when it comes to the value of plug-in vehicles. In June 2010, UK's Glass' Guide came to the conclusion that EVs would lose about 90 percent of their value after five years of ownership. That research group suggested at the time that EV values would suffer particularly because batteries would be worthless after half a decade.