PHEV 2025: T&E data reveals emissions discrepancies.
A Transport & Environment study of 800,000 PHEVs revealed that actual CO₂ costs are nearly five times higher than reported. Users could end up spending an additional ₂500 per year; the EU is tightening the electric vehicle consumption coefficient for the period 2025–2028.
Plug-in hybrid (PHEV) models were once seen as a "green" bridge between internal combustion engines and electric vehicles. However, real-world usage data compiled by Transport & Environment (T&E) from 800,000 vehicles in Europe reveals a significant gap between published and actual emissions figures. Actual CO₂ emissions can be nearly five times higher than reported by manufacturers, raising questions about both the environmental efficiency and operating costs of PHEVs.
The gap between testing and reality: data from 800,000 vehicles.
T&E noted that in 2021, the actual average emissions of PHEVs were 134 g/km, 3.5 times higher than the 38 g/km announced by the manufacturer. In the latest study, the difference is even greater: the announced figure was only 28 g/km, but the actual measured figure reached 139 g/km.
| Time | CO₂ (g/km) | Actual CO₂ (g/km) | Difference |
|---|---|---|---|
| 2021 | 38 | 134 | Approximately 3.5 times |
| Latest | 28 | 139 | Approximately 5 times |
According to T&E, the discrepancy in figures stems from actual usage differing significantly from the assumptions made during the certification process. The majority of owners do not charge their vehicles regularly or primarily use gasoline engines; even when fully charged, many vehicles prematurely activate the internal combustion engine during high-speed acceleration, uphill climbing, or in cold weather.
Why are PHEVs less green than people think?
- Charging behavior: many users do not charge regularly, so the vehicle runs on more gasoline than assumed during certification.
- Operating conditions such as acceleration, steep terrain, and cold weather cause the gasoline powertrain to intervene prematurely, reducing the time spent running purely on electric power.
- Assumption for testing: the computational models in the certification assessment estimate electricity usage rates higher than actual daily usage.
Economic and policy impacts
T&E estimates that each household using a PHEV could spend an additional €500 ($580) per year due to actual fuel consumption being higher than reported. On a macro level, some European governments have relied on PHEV sales to pursue their fleet emissions reduction targets. However, T&E argues that this "optimistic" calculation of PHEVs has helped some automakers avoid large fines, while the emission reduction benefits have not met expectations.
With Europe aiming to stop selling internal combustion engine vehicles by 2035, these results raise questions about the mediating role of PHEVs in the transition.
The EU will tighten the "electricity consumption coefficient" from 2025.
Current regulations assume a PHEV with a 60km electric range will operate in EV mode up to 80% of the time. The new framework will lower this percentage to be closer to real-world usage patterns.
| Implementation period | Assuming EV and PHEV driving time is 60 km. |
|---|---|
| Current | 80% |
| 2025–2026 | 54% |
| 2027–2028 | 34% |
However, T&E warns that even with the new calculation method, the difference between reported and actual emissions could still be around 18%.
What should PHEV users consider?
- Discipline in charging: environmental and cost benefits only materialize when the vehicle is charged regularly to maximize its pure electric range.
- Trip profile: if you frequently travel long distances, carry heavy loads, or drive in cold conditions, a gasoline engine will require more intervention.
- Expected consumption: The published WLTP figure may differ significantly from actual daily usage, depending on habits and operating conditions.
Conclusion: The bridge is incomplete.
Based on T&E's data, PHEVs are not as "green" as expected, with real-world operation differing significantly from the test assumptions. The gap in CO₂ consumption is nearly five times, resulting in higher costs for users and challenging government emission reduction targets. Tightening the "utility model factor" from 2025 is a necessary step, but T&E believes there is still a significant discrepancy. For buyers, the efficiency of PHEVs largely depends on charging discipline and specific usage conditions.
