I’m not disputing the results, but I would be really interested in a follow-up study that looks at why. From this data it would seem that only 10% or so of people with plug ins actually use the plug, which seems really odd. You have to pay massively more for it, and at least anicdotaly the dealers will try and steer you away from them allmost as hard as they do EVs. Given plug ins are often more expensive than both traditional hybrids and EVs, it seems really odd to spend a lot of money on somthing and then waste even more money to not use it.

Given the small battery size any wall outlet will charge them fine, which would seem to rule out infrastructure. So why does it seem that almost everyone who goes through the trouble and cost of getting one apparently not using it?

The only thing I can think of would be people believing that european electrical prices are higher than fuel prices, but while european electricity prices are higher so are gas prices.