by Unveiling the Environmental Myth
The green halo around plug-in hybrid vehicles is beginning to fade, and a new study by Transport & Environment only reinforces this trend. What was once considered the perfect transition from conventional engines to full electrification now appears less virtuous upon real-world examination.
According to the results of testing 800,000 cars, PHEVs in everyday European use emit almost five times more CO2 than official tests show.
Everyday Reality
For many years, PHEVs have been advertised as the perfect compromise between fully electric cars and traditional gasoline models. You can charge them when possible, drive in electric mode for short distances, and rely on gasoline for longer trips.
Newer PHEVs can travel on electricity more than twice as far as older models – in some cases up to 70 miles (113 km), and they might even be allowed to remain on the roads after the ban on internal combustion engines comes into effect in Europe from 2035.
However, in real life, many owners forget or are unwilling to charge them, instead using mostly gasoline. Even when the cars are charged, the study found that PHEVs quickly switch to internal combustion engines during moderate acceleration, on inclines, or in cold weather.
This means their electric systems were doing less work than regulators assumed during certification.
Divergence of Numbers
As it turned out, this gap is only widening. Back in 2021, T&E recorded real-world emissions of plug-in hybrids at 134 g/km, approximately 3.5 times higher than the official 38 g/km. In the latest study, the difference has increased: manufacturers now claim an average of 28 g/km, yet testing shows a much higher 139 g/km.
For consumers who bought a PHEV promising low emissions and lower running costs, the reality may turn out to be higher fuel bills and a significantly larger carbon footprint.
T&E told The Guardian that families could be overpaying up to 500 euros per year compared to if their car met the stated fuel consumption figures. For governments and regulators relying on PHEVs to meet fleet emission targets, the risk is that this tool is much less effective than anticipated.
According to T&E, automakers could have avoided billions in potential fines by relying on optimistic PHEV emission calculations.
Regulatory Changes and Their Limitations
Legislators are already familiar with this situation due to previous studies and are gradually implementing stricter rules that reduce the “utility factor” – the time during which PHEVs are assumed to operate in electric mode when calculating CO2 figures.
Under current rules, a PHEV with a 60 km (37 miles) range is expected to drive in electric mode over 80% of the time, although this figure will decrease to 54% in 2025/26 and to 34% in 2027/28.
But T&E argue that even after applying the 2027/28 framework conditions, an 18% gap between stated and actual CO2 emissions will remain.
This data points to a systemic problem that goes beyond individual models or manufacturers. The gap between laboratory tests and real-world operation calls into question the effectiveness of current certification methods, as well as the long-term role of hybrid technologies in transport decarbonization. The increase in electric range of new models does not solve the fundamental problem – driver behavior and operating conditions, which significantly impact final emissions.
