Report finds plug-in hybrids emit nearly as much pollution as gasoline cars

The hidden truth about hybrids

Plug-in hybrid cars were once seen as a green bridge between gas and electric power. However, new research suggests they may be polluting far more than previously thought, surprising both drivers and experts.

A new T&E analysis of EEA on-board monitor data reveals that real-world PHEV CO₂ emissions are, on average, 5 times higher than those reported under WLTP. This means plug-in hybrids may not be as clean or efficient as advertised.

What plug-in hybrids really are

Plug-in hybrid electric vehicles, or PHEVs, use both an electric battery and a gasoline engine. The idea was to give drivers the best of both worlds, electric driving for short trips and gas for longer ones.

However, this dual setup creates a significant gap between how these cars perform in tests and how they perform on actual roads. That difference is now at the center of a growing debate over emissions.

Official tests vs. real driving

During lab testing, plug-in hybrids are driven in controlled conditions that don’t reflect real-world habits. Drivers often rely more on gasoline power than assumed in those tests.

Across 127,000 PHEVs registered in 2023, the real-world CO₂ emissions averaged 135 g/km, which is 5 times the official WLTP figures. That’s a major difference that challenges automakers’ green claims.

Why emissions are higher

Researchers found the main reason emissions are higher is that PHEVs are rarely driven, mostly in electric mode. Press coverage of the dataset reports that WLTP assumes 84% electric driving, while real-world use averages around 27%.

This makes real-world pollution levels much worse than the numbers printed on brochures.

Engines that won’t stay off

Even when plug-in hybrids are running in “electric mode,” the gas engine often kicks in. The electric motors aren’t strong enough for high speeds or steep roads.

EEA data indicates engines supply power during one-third of the distance, even in ‘EV mode,’ yielding 68 g/km in that mode. So, even when drivers think they’re driving clean, they’re still polluting more than expected.

The cost to drivers

Plug-in hybrids don’t just pollute more—they also cost more to drive than most buyers realize. Hidden fuel use and frequent engine engagement result in many owners spending approximately €500 more per year on gas than expected.

That extra expense adds up quickly, especially for those who bought these cars expecting major savings. Instead of cutting costs, many PHEV owners end up paying more in both fuel and maintenance over time.

How automakers benefit

The emissions gap didn’t just mislead drivers—it helped carmakers save billions in penalties. Between 2021 and 2023, companies avoided paying large EU fines by reporting lower CO2 emissions on paper.

According to the Guardian, four major automaker groups dodged more than €5 billion in fines. By overstating the environmental benefits of their plug-in hybrids, these companies met climate goals without actually reducing pollution.

Consumers feel misled

Many drivers trusted automakers’ promises that PHEVs would be cleaner, cheaper, and better for the planet. Now, experts say consumers were misled by exaggerated claims about fuel savings and eco-friendliness, according to The Guardian.

Recent EU data show that PHEVs have an average CO2 emissions of approximately 135 g/km, compared to ICE vehicles at approximately 166 g/km, which is closer than the WLTP suggests, although not identical.

With higher purchase prices and hidden running costs, many owners are realizing the supposed benefits don’t match reality.

Bigger batteries, bigger problems

It might sound logical that bigger batteries mean cleaner performance, but that’s not always the case. Heavier plug-in hybrids need more energy to move, which makes them less efficient when running on gasoline.

T&E reports indicate that PHEVs with a range of 75 km or more emit more on average than those with a range of 45–75 km, likely due to the added mass and increased engine use. The added weight cancels out many of the supposed environmental advantages, making size a real drawback.

Real emissions by the numbers

The gap between lab tests and reality is striking. According to T&E, real-world data shows plug-in hybrids emit around 135 grams of CO2 per kilometer—nearly as much as gasoline or diesel cars, which average 166 grams.

Even when running in electric mode, hybrids still release about 68 grams of CO2 per kilometer. That’s far higher than what automakers report, revealing just how inflated official test results can be.

The Mercedes gap

Mercedes-Benz recorded one of the biggest differences between official and real-world emissions. Its GLE-Class plug-in hybrid produced more than six times the CO2 claimed in its lab-tested figures.

Other major automakers weren’t far behind, showing emissions roughly 300% higher than reported. These findings raise tough questions about testing honesty and whether consumers can trust the numbers shown in marketing materials.

The EU’s tough decisions

Europe plans to phase out new combustion engine cars by 2035, but automakers are fighting to keep hybrids in the mix. They want plug-in hybrids to still count as “clean” vehicles under upcoming regulations.

The EU is tightening its “utility factor” to better reflect how people actually drive, but carmakers oppose it. They fear stricter rules will make it harder to meet emissions limits and force faster adoption of full EVs.

Experts call it a ‘green illusion’

Environmental experts say the promise of plug-in hybrids was oversold. Lucien Mathieu from Transport and Environment even called them “one of the biggest cons in automotive history.”

He argues that PHEVs emit nearly as much as gas vehicles, even in electric mode. Weak regulations and misleading marketing, he warns, are hindering real progress toward zero-emission technology, such as fully electric cars.

The weight of false promises

For years, plug-in hybrids were marketed as a smart middle ground for eco-conscious drivers. However, mounting evidence suggests that these vehicles may actually be hindering progress toward cleaner transportation.

Their hidden emissions make it more challenging for countries to meet their climate targets and reduce pollution. Now, as awareness grows, many buyers are starting to question whether the higher prices and promises are worth it.

The political debate

The growing data has triggered major political debate across Europe. Countries with large auto industries, such as Germany, are pushing for flexibility in emissions laws to protect their carmakers.

Some German leaders even want to extend hybrid sales beyond 2035, citing concerns about jobs and the economy. But critics argue that delaying tough standards only benefits manufacturers, not the planet or consumers.

Want to make the smartest car choice? Learn about the key features to check on hybrids and electric cars before making your next move.

What drivers can do

Plug-in hybrid owners can still make minor adjustments to minimize their environmental impact. Charging their cars more frequently and relying on electric mode for short trips helps cut emissions and fuel costs.

Buyers should carefully consider long-term costs before selecting a hybrid. Comparing maintenance, charging habits, and real fuel use can reveal whether it’s truly worth the investment.

Thinking all hybrids work the same way? Toyota says not all hybrids are as real as they claim to be — find out what sets the true ones apart.

Want to stay ahead on the latest car news? Check out these must-read stories and get the inside scoop on new models, deals, and trends.

Read More From This Brand:

• Car lease deals available in August 2025
• Lexus previews new LFR sports car concept in 2025
• How the Camaro Z28 became a bargain muscle car

Don’t forget to follow us for more exclusive content right here on MSN

If you liked this story, you’ll LOVE our FREE emails. Join today and be the first to get stories like this one

This slideshow was made with AI assistance and human editing.