Is like to have a source for the statement that plug in hybrid never gets plugged in. Everyone I know who has one charges it over night and only runs it on petroleum occasionally.
43% of the private owners use the charging option, 18% of the company owned cars. However, due to tax incentives, 63% of all cars registered per year are company owned cars.
The incentives are that you get a substantial tax break if you register a plug-in (or electric) car - leading to the odd result that 40% of all Porsche Panameras registered are plug-in hybrid cars.
This is why I think more of the tax should be moved from buying to using. C02 tax for cars should be mostly at the pump when filling the tank, not when buying. A plug-in driven 10 000 km a year pollute more than any car driven 100 km a year.
So it should be taxed same as hybrid car if owner doesn't have charging station at home.
Some environment group argue that lower range PHEV is evil because it's just for cheat but I against. PHEV should cover daily use range (YMMV 30-60km?) but shouldn't need much because they have engine for fallback. Equipping mostly unneeded batteries is definitely bad for environment.