PHEVs Still Miss Official Emissions Targets by a Wide Margin, New Analysis Finds

Plug-in hybrids are still falling far short of the efficiency promises their official ratings suggest. According to a fresh analysis of 2024 real-world data, PHEVs on European roads produced emissions roughly six times higher than the figures recorded under the WLTP laboratory test. The finding reinforces long-standing concerns that the plug-in category’s climate credentials have been systematically overstated.

The root of the problem lies in how the market has evolved. Automakers have been pushing heavier, more powerful and longer-range PHEVs, but many of these vehicles lack the electric motor output needed to actually drive on electricity alone for meaningful stretches. On average, PHEVs are driven in pure electric mode only 27% of the time, according to the data. Models with an electric range above 70 kilometers showed a 52% gap between real-world and official emissions, compared with 35% for models below that threshold. The average PHEV range grew from 58 km to 75 km between 2021 and 2024, meaning that longer-range variants accounted for the majority of the 2024 discrepancy.

One metric that appears to track real-world performance more reliably than range is the ratio of electric to combustion power. PHEVs with 25% more electric than combustion power emit just 95 gCO₂/km in real-world conditions — roughly a third of the average PHEV. This suggests that how a PHEV is engineered matters more than how far its battery can theoretically carry it.

A planned correction to the utility factor (UF) methodology, scheduled for November 2026/27, is intended to bring official accounting closer to actual emissions. Evidence from the previous 2025 UF correction suggests the approach works: some automakers increased electric range from 63 km to 117 km to offset the adjusted figures, and upgraded 2026 models saw average battery capacity rise from 14 kWh to 24 kWh. That battery increase added only about 2% to vehicle prices, while roughly three-quarters of the official CO₂ increase caused by the corrected UF was offset — keeping many models below the 50 gCO₂/km mark.

T&E’s projections indicate that by 2030, electric ranges of around 140–220 km would keep PHEVs at or below 50 gCO₂/km. The analyst behind the report notes that freezing the UF at the 2025/26 correction would underestimate real-world emissions by 56% and would reduce projected BEV sales by 13 percentage points in 2030 and 18 percentage points in 2035. On the taxation side, the picture is uneven: 24 of 27 EU member states offer PHEVs some form of preferential tax treatment, but only 12 apply a CO₂ threshold of 50 gCO₂/km or stricter, and just Portugal and Spain require both a CO₂ limit and a minimum electric range. In 19 member states, the annual tax difference between a corporate PHEV and a battery-electric vehicle is negligible, which blunts the signal for buyers to choose better-performing models.