There is a systemic gap at the core of Europe’s plug-in hybrid policy, and it has now been measured at scale.

Using real-world fuel consumption data from approximately 980,000 plug-in hybrid passenger cars collected under the EU’s official on-board fuel consumption monitoring (OBFCM) system, the Fraunhofer Institute for Systems and Innovation Research (Fraunhofer ISI) has delivered the largest empirical assessment of PHEV performance to date.

The finding is blunt. While WLTP certification values typically range between 1.0 and 1.3 liters per 100 kilometers, the monitored fleet averages 6.0–6.2 l/100 km in real-world use, a divergence of 300–500%.

False assumptions

The cause lies in assumptions about electric driving. EU certification embeds utility factors implying that 70–85% of PHEV kilometers are driven electrically.

Fraunhofer’s dataset shows that when measured strictly as kilometers driven with the combustion engine fully off, the average electric share is only 27–31%. In other words, roughly two-thirds of all kilometers are still driven by combustion engines.

The arithmetic is unavoidable. A vehicle certified at 1.2 l/100 km cannot meet that figure if only one-third of its driving is electric. At around 6 l/100 km, the average European PHEV operates in the same fuel-consumption band as many conventional hybrids — and in some cases above them.

Where electric use collapses

The dataset shows pronounced dispersion between manufacturers. Premium and performance-oriented brands consistently sit above the fleet average in real-world fuel consumption, often by a wide margin.

Based on aggregated brand-level fuel consumption distributions and inferred electric driving shares, the upper end of the least-charged PHEV segment includes model families that frequently exceed 8–10 l/100 km in real-world operation. This implies electric shares well below the 27–31% fleet average and, in some cases, likely under 20%.

Indicative high-consumption / low-electric-use segment (real-world averages frequently ≥8 l/100 km):

1. Porsche performance PHEVs — ~9–11 l/100 km
2. Ferrari plug-in models — ~10–12 l/100 km
3. Maserati plug-in hybrids — ~9–11 l/100 km
4. Land Rover / Range Rover PHEVs — ~8–10 l/100 km
5. Mercedes-Benz larger PHEVs — ~8–10 l/100 km
6. BMW performance PHEVs — ~8–10 l/100 km
7. Volvo larger PHEVs — ~8–9 l/100 km
8. Audi high-power PHEVs — ~8–9 l/100 km
9. Jaguar PHEV models — ~8–9 l/100 km
10. Subaru plug-in variants — ~7–9 l/100 km
11. Lexus luxury PHEVs — ~7–9 l/100 km
12. Cadillac plug-in hybrids — ~8–10 l/100 km
13. Infiniti plug-in models — ~8–10 l/100 km
14. Chrysler Pacifica PHEV — ~7–8 l/100 km
15. Jeep Grand Cherokee PHEV — ~8–9 l/100 km
16. Ford high-spec PHEVs — ~7–8 l/100 km
17. Volkswagen larger PHEVs — ~6–8 l/100 km
18. Peugeot 3008 PHEV (higher-use groups) — ~6–8 l/100 km
19. Opel/Vauxhall PHEVs — ~6–8 l/100 km
20. Renault plug-in hybrids — ~6–8 l/100 km

By contrast, several mainstream PHEVs from Toyota, Hyundai, and Kia average 4–5 l/100 km in real-world driving, implying electric shares of 40–50%, though still well below regulatory assumptions.

The behavioural multiplier

Usage patterns amplify the divergence. Independent European research shows private PHEV owners average 45–49% electric driving, corresponding to 4.0–4.5 l/100 km.

Company-car drivers — a significant share of EU registrations and especially in Belgium — average just 11–15% electric use, with fuel consumption rising to 7.5–8.5 l/100 km. This corporate undercharging effect materially shapes the fleet average.

In practical terms, a poorly charged PHEV combines the weight and cost of electrification with the fuel consumption of a conventional vehicle.

A well-optimised full hybrid (HEV), typically consuming 4–5 l/100 km without reliance on charging behavior, may therefore deliver real-world efficiency comparable to or superior to that of a conventional vehicle. Battery-electric vehicles eliminate tailpipe emissions entirely.

Regulatory Exposure

The Fraunhofer study does not merely document a performance gap; it evaluates regulatory consequences. Even after adjustments introduced in 2025, EU fleet compliance calculations continue to rely on laboratory-based utility factors that overstate real-world electric operation. A further revision planned for 2027 would narrow the gap but may not eliminate it.

More fundamentally, because compliance is based on certified rather than measured fuel use, manufacturers receive substantial CO₂ credits for vehicles that, in practice, operate predominantly on combustion power.

If this structure remains unchanged, Europe risks embedding a technology whose average real-world performance delivers far less emissions reduction than assumed, potentially slowing, rather than accelerating, decarbonisation.

Industry Accountability

The responsibility does not rest solely with drivers. Manufacturers promoted PHEVs as near-electric solutions while benefiting from regulatory assumptions that credited high electric use. Those assumptions helped meet fleet CO₂ targets and reduce compliance costs.

With average electric driving closer to 27–31% at fleet level — and much lower in parts of the premium segment — the credibility gap is structural. It reflects regulatory design, product strategy, and market positioning.

With nearly one million vehicles analysed, the debate moves from speculation to evidence. The central question is no longer whether plug-in hybrids can work under ideal conditions. The question is whether climate policy should continue to reward theoretical electric capability or verified real-world performance.