Testing by Emissions Analytics resulted in an average efficiency of 37.2mpg for PHEVs with their battery depleted. As many of them also have smaller fuel tanks to make space for the battery , it could be as frustrating to live with as it is costly to run.
However, you don’t need to be town-bound for them to make sense. Using that Emissions Analytics figure and UK average fuel and flat-rate home electricity prices, a PHEV could match fuel costs of a 55mpg diesel if only a third of its annual mileage was on battery power. Plus, unlike with the diesel, you would be able to do all of your urban driving without any exhaust fumes.
PHEV drivers in flats and rental properties can claim financial support to install home chargepoints, and there’s no tax liability for plugging in at work if your employer will let you. However, you will also need a suitable Type 2 charging cable; not all PHEVs include this, having it instead as a £200-300 extra.