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New tests suggest plug-in hybrids emit ‘more pollution than advertised’

The tests found that even when the cars had a fully charged battery and were driving in optimal conditions, emissions were still 28-89% higher.

Plug-in hybrid cars might not be as green as manufacturers let on. Tests on three of the most popular plug-in models reveal emissions are far higher than advertised, the campaign group Transport & Environment said.

Plug-in hybrids can be plugged in to charge their on-board batteries, and driven in ‘zero emission’ mode for short journeys. An accompanying petrol or diesel motor provides back-up power for longer distances.

In August the group commissioned Emissions Analytics to test three plug-in hybrids: the BMW X5, the Volvo XC60 and Mitsubishi Outlander – the top selling plug-in model in the UK last year – to find out whether ‘real world’ emissions on normal roads matched advertised levels.

The tests found that even when the cars had a fully charged battery and were driving in optimal conditions, emissions were still 28-89 per cent higher than advertised. On an empty battery, they emitted three to eight times more than official values.

The results back up previous findings from the International Council on Clean Transportation, which last year found the real-world CO2 emissions from plug-in hybrids were typically two-to-four times the measurements given in their approval process.

Carmakers argue plug-in hybrids are greener than petrol and diesel cars, while the built-in fossil fuel engine allays any fears of ‘range anxiety’ that could put people off adopting electric technology.

But T&E says hybrids are often little better than petrol or diesel cars. It wants the UK and EU governments to stop subsidies and incentives for the technology. Julia Poliscanova, senior director for clean vehicles at T&E, said: “Plug-in hybrids are fake electric cars, built for lab tests and tax breaks, not real driving. Our tests show that even in optimal conditions, with a full battery, the cars pollute more than advertised. Unless you drive them softly, carbon emissions can go off the charts.”

UK sales of plug-in hybrids have trebled in the last year, despite subsidies being curtailed. Last week the UK government announced a plan to phase out the sale of new petrol or diesel cars by 2030. But the policy included a five-year extension for plug-in hybrids.

T&E said the Government should reconsider its 2035 phase-out date for the technology: “There should be a single date to end the sale of all cars that have an engine including plug-in hybrids,” it said in September. “The Government should not be treating plug-in hybrids as in any way special as in real-world conditions (rather than lab tests) they have CO2 much more comparable to a modern conventional cars, and for plug-in hybrids that are not charged, significantly worse.”