Car firms defend PHEVs amid evidence of high CO2 output

BMW, the UK’s third-biggest seller of PHEVs in the UK so far this year, also pointed to the official tests in its defence of the technology, which requires owners to charge the battery via a plug to gain the full benefit. “These tests show clearly that plug-in hybrid technology, when the vehicles are charged regularly as intended, can save significant fuel consumption and emissions over the equivalent petrol or diesel models,” the company told Autocar in a statement.

JLR meanwhile pointed to the chunky batteries in Range Rover and Range Rover Sport plug-in hybrids. “Typical Range Rover customers will be able to complete up to 75 per cent of trips using electric power only if they begin each journey with a full charge,” the company said in a statement to Autocar. ““Plug in hybrids offer clients a great combination of performance, fuel economy, low emissions, with zero emissions at the tailpipe.”

Automotive supplier lobby group CLEPA took issue with the results. “The Commission’s recent study does not account for technological progress,” the organisation said in an email to Autocar. It defended the technology as an important addition to the choices available to consumers as they make their shift to lower CO2 technologies. “Plug-in hybrid electric vehicles should be seen as a bridge towards electrification, not a U-turn,” it said.

Mercedes-Benz pointed the blame firmly at the tests themselves, calling the measurement process “unrealistic” and flagging upcoming changes. “The utility factor consideration in the WLTP is unrealistic: the main reason for this is that the assumed driving and charging behaviour deviates from real customer behaviour,” the company told Autocar in a statement.

Mercedes also referenced its own data that it said showed PHEVs “have significantly lower CO2 emissions than corresponding combustion engine models” even without recharging.

The PHEV hasn’t been mortally wounded by this report – far from it. As CLEPA points out, the data is relatively out of date, given it was harvested from cars first registered in 2021. Many car makers didn’t report data, meaning the numbers were dominated by just a handful of brands. The plug-in hybrid dataset consisted primarily of Mercedes-Benz (39%), Volvo (19%), and Ford (16%) vehicles. The European Commission admitted the flaws. “At this point, it is too early to identify trends in the gap size as data is only available for one year,” the commission said.

The purpose of the data collection is to work out whether authorities in the European Union (and the UK, given it also uses WLTP figures to calculate CO2) need to change the way they calculate CO2 figures. 

That’s already going to happen. The “mismatch” between the so-called utility factor – that is, the percentage of time the test assumed the car will be driven in electric mode – and the actual drive time is going to be narrowed from 2025. Then, the test will assume the car will be driven half its time on electric, rather than the current 70-85% assumption. A further change is expected in 2027, informed by another interrogation of figures this year.

That’s going to remove some of the more fantastical CO2 and MPG claims from new plug-in hybrids sold. For example, reducing the expected electric miles driven in the changed 2025 test (the so-called Euro 6e-bis) will increase the recorded CO2 for the BMW X1 xDrive25e, a plug-in hybrid SUV, from 40g/km to 96g/km, the International Council of Clean Transportation (ICCT) calculated. The proposed change in 2027 would increase that again to 122g/km.

With those numbers, the PHEV would wither and die. The cost to integrate an expensive battery and electric motor into a combustion engine car would blow the business case out of the water without the attendant low CO2 figure to reduce average emissions and offer some tax benefits to the customer

However, car makers are responding by increasing the battery size to give a greater electric-only range, meaning that they’ll be able to match the pace of the WLTP changes to the electric ‘utility factor’.

Battery sizes grew by a “massive” 27% between August 2022 and the same month last year, according to the most recent study by metals and minerals consultancy Adamas Intelligence, bringing the average battery size to 21.8kWh.

Examples include Mercedes’ recent overhaul of the GLC to increase the battery size in the 300e PHEV to 24.8kWh from 13.5 kWh, boosting the claimed electric-only range to 81 miles from 28 miles. The pack – which is slightly larger than that fitted to the Mk1 generation Nissan Leaf EV – has also gone into the firm's new E300e and C300e.

Meanwhile, the Volkswagen Group has increased the size of the battery in its new plug-in hybrid cars on its MQB Evo platform from 13kWh to 19.7kWh, including the VW Tiguan, VW Passat, VW Golf, Skoda Kodiaq and Skoda Superb. In the Golf, that gives a claimed electric range of 62 miles.

Volvo meanwhile shared its own data showing that the effect of increasing battery size on its plug-in hybrids was to increase the number of journeys travelled on purely electric. That went from 38% in 2021 model year PHEVs with an effective electric range of around 31 miles to 50% in 2023 model year cars with an effective range of around 40 miles.

The downside of increase battery side however is that it makes plug-in hybrids even more expensive, given the need to package an even bigger battery along with electric motor and regular combustion engine. It’s probably no co-incidence that three best-selling plug-in hybrid brands – Land Rover, Audi and BMW – in the first three months of UK sales, were all premium. The Audi A3 was the UK’s top selling PHEV in the first three months.

The technology has even pulled in luxury brands including Bentley and Aston Martin, both of whom have pushed back plans to launch electric cars in favour of an expanded plug-in hybrid range. The technology suits customers who "want some electrification but still have the sports car smell and feel and noise,” Aston Martin chairman Lawrence Stroll told investors recently.

The poor real-world figures versus the test results are partially linked to their strong fleet usage. In the first half of this year, three-quarters of all plug-in hybrids were bought by companies. Incentivised by the low CO2 figure extrapolated from the test, company car drivers often lack the follow-on incentive to actually charge the battery and achieve the quoted figure, or even get close to it.

In fact, company cars are driving on electric just 11-15% of the time, according to the green transport pressure group T&E, meaning there’s still a way to go before the real figure is reached. “This is particularly problematic as company cars make up 71% of new PHEV sales,” T&E said.

If PHEVs were only a European phenomenon, they might have died on the development table, squeezed on one side by rising sales of hybrids and on other by EVs as they become cheaper. In the UK, despite the sale growth, they still accounted for just a 7.8% market share in the first three months, compared with 15% for EVs and 14% for hybrids.