The article is horribly unclear: it seems to say that PHEVs are no good, but “the main reason for the higher-than-stated fuel usage was …that the PHEVs use two different modes, the electric engine and the combustion engine”. Well, so do non-plugin hybrids. I doubt they’re saying that plug-in hybrids are worse than non-plugin, but you might guess that from the title.
The article states that Porsche PHEVs used 7 liters per 100 miles (33.6mpg), but Kia/Toyota/Ford/Renault used “85% less” (1.05L/100k or 223mpg… maybe about right if driven 75% from plug-in energy).
Porsche mentioned “different usage patterns”. I can buy that a typical Prius owner is plugging-in every night, filling low-rolling-resistance tires to 54psi and driving like grandma, and a typical Porsche owner… isn’t. If you want apples-to-apples, then compare a gas Corolla vs a Prius vs a Plug-in Prius, where the cars are from the same city/suburb, and similar owners (e.g.: no ubers, no regional sales reps).
This “study” is evaluating real-world use of one class of vehicles, and not other vehicle types; then using the dismal ways some people drive to imply that this particular class of vehicles is the problem.
The way I read it is:
Sadly, it sounds like Porsche drivers may fall into the first category and Toyota drivers in the second. And there are enough Porches to skew the MPG of the whole PHEV class.
(it’s also possible that Porsche/VW/Audi just make PHEVs that score well on gov’t tests but poorly in the real world, though I’d lean towards the drivers. But the article title really implies that all PHEVs get shockingly bad mileage)