While most hybrids are said to use one to two litres of fuel per 100km, a study claims they need six litres on average
Plug-in hybrid electric cars (PHEVs) use much more fuel on the road than officially stated by their manufacturers, a large-scale analysis of about a million vehicles of this type has shown.
The Fraunhofer Institute carried out what is thought to be the most comprehensive study of its kind to date, using the data transmitted wirelessly by PHEVs from a variety of manufacturers while they were on the road.
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According to the study, the vehicles require on average six litres per 100km, or about 300%, more fuel to run than previously cited.
The scientists of the Fraunhofer Institute found that the main reason for the higher-than-stated fuel usage was due precisely to the fact that the PHEVs use two different modes, the electric engine and the combustion engine, switching between both. Until now it has been claimed by manufacturers that the vehicles used only a little or almost no fuel when in the electric mode. The studies showed that this was not in fact the case.
The issue isn’t really that the estimate is wrong, it’s that it’s wrong by an enormous amount – and one that’s been increasing every year. I don’t think that the study is trying to say that these vehicles are inefficient as some kind of absolute judgment, but that they’re less efficient than estimated (although there are big differences based on vehicle make and model).
I don’t think the problem really lies with manufacturers, it’s that the current tests aren’t accurate enough to predict real-world usage closely enough. Although, driver input is mediated by computer systems and if on-board systems are being too aggressive in switching over to ICE, I suppose that’s a manufacturers problem.
Really, they’ve been doing these very large studies for a long time. The sample size is large enough to capture the full diversity of driving styles and it cannot be a few outliers skewing results. Since 2012, the disparity between estimated and observed fuel usage has grown every year. Why? Why is it changing and why is it always changing in the same direction?
It getting worse over time I would think is partially a function of customer mix changing.
You start with early adopters who are more eco conscious and then now entering mainstream, and also people choosing plug-ins for performance purposes.