New 2025 emissions test targets 'misleading' plug-in hybrid efficiency figures

• Stricter emissions testing for plug-in hybrids
• Benefit-in-kind tax rates set to increase
• In effect from January 1st 2025

Stricter emissions testing for plug-in hybrid (PHEV) cars is coming into force this year in an effort to correct their “unrepresentatively low official CO2 emission values”, according to the International Council on Clean Transportation (ICCT).

The new testing is expected to have a big impact on the company car benefit-in-kind (BiK) tax rates for plug-in hybrid cars, which are based on CO2 emissions. All new PHEV models launched from January 1st 2025 will be subjected to the new testing rules, while existing models will need to be retested by December 31st 2025 in order to remain compliant.

How is the emissions test changing for PHEVs?

Studies have shown that the real-world fuel consumption of PHEVs doesn’t align with official test results when a vehicle is approved for road use. As a result, many PHEVs are emitting more CO2 than their official figures would suggest, which the ICCT says “undermines the European Commission’s CO2 reduction targets and misleads consumers”.

The hope is that the new testing procedures will represent the fuel consumption and CO2 emissions of PHEVs more accurately.

Under the outgoing ‘Euro 6e’ testing system, PHEVs were analysed over a distance of 800km (497 miles), driving under electric power and with the battery fully depleted. The new ‘Euro 6e-bis’ tests see this distance increased to 2,200km (1,367 miles), with adjustments made to reflect how PHEVs spend less time in electric-only mode than originally predicted.

What does this actually mean for car buyers?

Those changes are all well and good, but how will they impact car buyers in the real world? Thanks to an example provided by the ICCT, we can see just how significant these changes will be for buyers of plug-in hybrids – especially company car drivers.

The BMW X1 xDrive25e, a popular plug-in hybrid SUV, was analysed under the new testing procedure and its official CO2 emissions figure increased from 45g/km to 96g/km. As a result, it would now sit in the 24% benefit-in-kind band, up from 8% under the outgoing testing.

That’s a comparable figure to some of today’s efficient pure-petrol models, and would see monthly BiK payments increase dramatically.

When does the new testing come into effect?

The new Euro 6e-bis standard came into force on January 1st 2025 for all new PHEV models launched from this date onwards. PHEVs that are already on sale will need to be retested under the new standard by December 31st 2025 in order to remain on sale.

There is currently no plan to backdate the emissions testing and revised BiK bands for existing owners of PHEVs – the updated rules only apply to brand new cars. 

The new Euro 6e-bis standard is scheduled to be superseded by even tougher ‘Euro 6e-bis-FCM’ testing in 2027. This will see the testing distance increased from 2,200km to 4,260km (2,647 miles). Under these rules, the same BMW X1 would be rated at 122g/km, potentially meaning further BiK rate increases are in store.

Read more about the changes to the UK’s VED car tax system coming in April 2025…