Plug-in hybrids emit almost as much CO2 as petrol cars, European fleet data analysis finds

Real-world emissions far above lab figures

Plug-in hybrids, long marketed as a bridge to full electrification, are emitting nearly as much carbon dioxide as conventional petrol and diesel cars, according to an analysis by the Brussels-based advocacy group Transport & Environment based on European Environment Agency data. Reporting on the study by Mexico Business News found the analysis covered 127,000 PHEVs registered in 2023, whose real-world CO2 emissions averaged 135 g/km, compared with 166 g/km for petrol and diesel vehicles. ¹

Jalopnik reported the same study, citing the T&E finding that in the real world plug-in hybrids emit 135 g/km on average against 166 g/km for petrol and diesel cars, using fuel-monitor data gathered by the European Environment Agency from vehicles registered in the European Union in 2023. That result is nearly five times the emissions suggested under laboratory conditions: instead of the 75 per cent reduction official tests indicate, the study found PHEVs achieve only about 19 per cent lower emissions than conventional cars. ¹³

T&E cars director Lucien Mathieu was blunt about the result. 'Plug-in hybrids are one of the biggest cons in automotive history. They emit almost as much as petrol cars. Even in electric mode, they pollute eight times more than official tests claim,' he said, adding that after a decade PHEVs had never delivered. ¹

Why the gap between tests and reality is so wide

The study found that even when operating in electric mode, PHEVs consumed an average of 3 litres of petrol per 100 km, corresponding to 68 grams of CO2 per kilometre, about 8.5 times higher than official test reporting. Mexico Business News reported that insufficient electric motor power at high speeds or on steep inclines forces the combustion engine to run for roughly one-third of the distance covered in electric mode. ¹

Jalopnik reached the same conclusion in its coverage, noting that electric drive motors often lack the power to propel the vehicle in all conditions, with the petrol engine compensating and burning up to three litres per 100 kilometres even in electric mode. The outlet also cited T&E on the trend towards longer electric ranges: bigger batteries make the vehicles heavier, so they burn more fuel in engine mode and consume more energy when driven on battery. ³

That weight effect showed up directly in the data. Mexico Business News reported that long-range PHEVs with larger batteries emitted more CO2 than shorter-range models, with vehicles offering an electric range above 75 km showing higher average emissions than those with ranges between 45 and 75 km. ¹

The Australian picture: charging behaviour decides everything

ABC Science reported that a plug-in hybrid's actual emissions depend mostly on user behaviour rather than engine size or other features. A user who depletes the battery daily and recharges most nights might emit one-fifth of an equivalent petrol or diesel car, while someone charging only a couple of nights a week emits far more. The difference between regular and irregular charging amounts to a bit more than $1,000 in petrol a year, or roughly $20,000 over 15 years, according to the ABC's figures. ²

The most recent European research found that, on average, PHEVs are mostly driven with empty batteries, emitting almost five times more CO2 than official European Union estimates, ABC Science reported. The ABC noted that devices measuring fuel consumption are mandatory for new cars in Europe, which is what made the analysis possible. ²

Australian data is more contested. The Electric Vehicle Council referred the ABC to a 2024 survey of 625 private PHEV owners which found most plugged in every night and drove in EV mode about 65 per cent of their trips. 'Australians predominantly drive PHEVs in EV mode and charge them regularly,' EV Council chief executive Julie Delvecchio said. BYD, the largest PHEV seller in Australia, told the ABC its servicing odometer data showed PHEVs driven about half the time in EV mode, which product engineering manager Harry Li attributed to better access to home charging in lower-density housing and higher rooftop solar uptake. ²

But T&E data analysis director Thomas Earl told the ABC that Australian PHEVs might emit even more than European ones, because they tend to be heavier and are driven longer distances. He argued that better access to off-street parking did not necessarily mean more frequent charging, noting Europe has much higher public charging availability. ²

Fleet users are the weak link

ABC Science reported that employees driving company-car PHEVs may be the least likely to recharge, with studies from Europe and the United States showing company-car users charge less because they have no financial incentive to save fuel. Mace Hartley, head of fleet industry peak body the Australasian Fleet Management Association, told the ABC that fleet managers struggle to get employees to plug in: 'with fleets you have to drag people kicking and screaming to recharge.' He estimated maybe 20 per cent of fleet users plug their vehicles in, and said some large fleets that switched to PHEVs found fuel use went up. Business fleet sales account for about half of all new cars sold in Australia. ²

What it could mean for Australia's emissions targets

More than 60,000 PHEVs have been sold in Australia over the past two years, partly due to federal government tax incentives for low-emission cars, and the category now accounts for about 5 per cent of new car sales, ABC Science reported. Exclusive modelling for the ABC by Transport Energy/Emission Research, an independent Australian consultancy, assumed PHEVs would account for half of EV sales from 2025 to 2035 before declining to zero by 2050. If users recharge irregularly, and EV-mode driving sits at 20 per cent of kilometres rather than the 80 per cent assumed, the modelling adds more than 100 million tonnes of CO2-equivalent for 2025 to 2050, comparable to a full year of emissions from all cars, vans, buses, motorcycles and trucks in Australia. ²

'The fleet-wide impacts of increased PHEV sales strongly depend on the average [share of driving in EV mode],' TER research director Robin Smit told the ABC. He also raised a regulatory concern: under the updated New Vehicle Efficiency Standard, suppliers of low-emission vehicles earn tradeable carbon credits, and PHEVs are counted as low-emission on paper under a method that assumes regular recharging. 'Because of the way [this regulation] is designed and implemented now, it is more likely that PHEV sales will replace the sale of BEVs,' Dr Smit told the ABC, arguing this reduces pressure on suppliers to sell more fully electric cars. ²

In Europe, the same regulatory question is live. Mexico Business News reported that the European car industry is lobbying to continue PHEV sales beyond the EU's 2035 zero-emission vehicle deadline and to remove the utility factors that adjust CO2 ratings for real-world driving. Mathieu warned that weakening the rules would let carmakers flood the market with expensive, polluting PHEVs and undermine investment certainty for fully electric vehicles. ¹