Plug-in hybrids do not always load.
A study now shows how much the consumption of part-time electric vehicles deviates from the factory specifications
Photo: Maskot / Getty Images
On paper they combine the best of two worlds: silent electric driving in the city and on the daily commute to work combined with an internal combustion engine for longer trips, for example on vacation.
The entire package of externally chargeable plug-in hybrids is sweetened by high state subsidies, when buying a part-time electric vehicle, the federal government gives up to 4500 euros.
This makes the vehicles popular; in the first half of the year, 3.5 percent of all newly registered passenger cars in Europe were plug-in hybrids.
The ecological benefit of the vehicles is controversial, as it depends on how often they are actually charged.
Always stay up to date?
Driving reports, analyzes, the latest news: you won't miss any articles from the Mobility section of SPIEGEL.
How to enable your notifications Right arrow
A study by the Fraunhofer Institute for Systems and Innovation Research (ISI) and the International Council on Clean Transportation (ICCT) has now examined this question.
To do this, they used data from over 100,000 plug-in hybrid vehicles from scientific studies, from platforms such as Spritmonitor.de or MyMPG, as well as from companies that provided the consumption values of their company cars.
Data from around 1400 vehicles were available from Germany, including 1385 private cars and 72 company cars, plus values from 10,800 company cars from the Netherlands.
The results of the investigation are sobering:
"On average, the real fuel consumption and CO2 emissions of plug-in hybrid vehicles for private owners in Germany are more than twice as high as in the official test cycle," explains Patrick Plötz, Head of the Energy Business Unit at Fraunhofer ISI.
The deviation is even higher for company cars, three to four times the values from the NEDC test cycle, according to which most of the vehicles examined were certified.
Even in the more realistic, newer WLTP cycle, the study shows that the deviation remains roughly the same.
According to the study, the difference between test bench values and real consumption is higher for plug-ins than for pure combustion engines.
This is mainly due to the so-called "Utility Factor" (UF).
This value indicates how often the hybrids are driven purely electrically.
While the electric share of private plug-in hybrids averaged 69 percent in the NEDC cycle, it was significantly lower in real operation.
There, only 37 percent of the routes were covered purely electrically.
For the examined vehicles from Germany, the value was slightly higher at 43 percent.
This difference was even greater for company cars.
While the "utility factor" of these models in the NEDC cycle was an average of 63 percent, company cars only covered 20 percent of the kilometers driven purely electrically in real operation.
In the small group of German company cars examined, the figure was only 18 percent, in the Netherlands it was 24 percent.
According to the researchers, the low proportion of purely electric driving is due to the infrequent charging processes.
According to the study, drivers of private plug-ins only charge their car on three out of four days of driving.
Company cars are connected to the power grid even less often and only charged on every other day of driving.
However, plug-in hybrids only achieve the promised low consumption values - and thus also low CO2 emissions - if they are charged as often as possible.
Other funding is intended to make electric driving more attractive
ICCT director Peter Mock is therefore in favor of changing funding for externally chargeable hybrids.
He recommends that "when promoting plug-in hybrid vehicles, preference should be given to models that have a long electric range and, at the same time, low internal combustion engine performance."
According to the study, there is a connection between CO2 emissions on the one hand and the electric range and the system performance of the drive train on the other.
Power limit for combustion engines as a solution
Ten kilowatts less power also reduce CO2 emissions by two to four percent.
If, on the other hand, the electric range is increased by ten kilometers, the consumption figures also improve by eight to 14 percent.
The authors of the study therefore not only see the state as obliged to link purchase premiums and lower company car taxation to evidence of predominantly electric driving.
According to the study, manufacturers should also act and increase the electric range of the models from today's average of 50 kilometers to 90 kilometers and at the same time limit the power of the internal combustion engine.
In this way, the industry could motivate drivers to drive purely electrically more often, the researchers argue.
However, they should not be heard by the manufacturers - because they would then have to do without supposedly economical plug-in sports cars such as the 600-hp Polestar 1 or the 560-hp Porsche Panamera 4S E-Hybrid.
Icon: The mirror