Why are PHEVs less efficient than normal hybrids?

I have read your report about poor real life mpg for plug-in hybrids if not plugged in. Why are they less efficient than conventional hybrids if used in the same way?

Asked on 16 November 2018 by GEORGE COOKE

Answered by Andrew Brady
Plug-in hybrids tend to have bigger batteries and smaller engines than conventional hybrids and are designed to be charged regularly. If they're not charged, they're woefully inefficient as they're effectively an underpowered car carrying an awful lot of weight. It's also worth noting that, during the old NEDC fuel economy tests, plug-in hybrids would start with a fully-charged battery. This would result in a large disparity between the official and real-life figures if owners didn't charge them regularly. Our report was based on thousands of fuel economy figures provided by readers: www.honestjohn.co.uk/real-mpg/
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