Euro 6e-bis: plug-in hybrid CO2, recalculated

Euro 6e-bis is the European standard that, since 2025, recalculates the official CO2 of plug-in hybrids. It touches neither the engine nor the battery. It changes one distance in a formula, and that distance roughly triples the figure on the certificate. In Belgium, it is the employee's benefit in kind that absorbs the difference.

Euro 6e-bis changes a distance, not an engine

At the dealership workshop I saw customers comparing two order forms for the same plug-in hybrid, six months apart, unable to understand why the CO2 had doubled. They assumed the manufacturer had changed the engine. Nothing had changed at all.

The WLTP procedure measures a plug-in hybrid (PHEV) twice: with a full battery, until it is depleted, then with an empty battery. The two results are then blended with a coefficient, the utility factor, meant to represent the share of kilometres driven on electricity. I covered this in detail in the article on plug-in hybrid real-world fuel consumption. Keep one thing in mind: that coefficient depends on the electric range, and on a parameter you never see, the normalisation distance.

That parameter is what Regulation (EU) 2023/443 changed. The utility factor curve was built for Europe in 2014, from travel statistics, with a normalisation distance of 800 km (Commission technical report, November 2014). Euro 6e-bis raises it to 2,200 km. The next step, called Euro 6e-bis-FCM, will raise it to 4,260 km.

The longer that distance, the more range a car needs to reach the same utility factor. With the same battery, the assumed electric share drops, the combustion share rises, and the weighted CO2 follows.

According to the ICCT, which dissected the text in December 2022, 2,200 km matches the average use observed on privately owned plug-in hybrids, and 4,260 km the average of the whole European fleet, company cars included. Company cars are precisely the ones that get plugged in least.

When does Euro 6e-bis apply to your car?

It all depends on two dates: the model's type approval and the first registration of your particular car. A model approved in 2023 and registered new in February 2026 had to be re-approved, and its certificate carries the new figure.

The Belgian threshold comes from the law of 18 December 2025, published in the Belgian Official Gazette on 30 December 2025, and circular 2026/C/10 of 7 January 2026 explains how to apply it. A small irony: the published law text refers to a "Euro 6e1-bis" standard, a typo the circular itself points out.

A car that is already registered never changes its figure. A 2024 Kia Niro 1.6 GDi PHEV keeps the CO2 on its certificate, between 19 and 25 g/km depending on the version according to autotijd.be, even if resold in 2028. It is a plug-in hybrid whose drivers log 2.87 l/100 km across 309 cars (Spritmonitor, 26 September 2026, full-battery and empty-battery trips mixed), and whose traction battery is covered for 7 years or 150,000 km on pre-2026 cars, 8 years or 160,000 km after that.

I redid the utility factor calculation

No spec sheet publishes the utility factor. The formula, however, is public: an exponential with ten coefficients, set in the 2014 report, applied to the electric range divided by the normalisation distance. I ran it for five electric ranges and the three distances, assuming a plug-in hybrid that emits 140 g/km with an empty battery (about 6.1 l/100 km of petrol) and almost nothing with a full one.

Simplified calculation, done on 14 October 2026: the regulation applies the formula phase by phase over the full-battery test, and a real car emits a little CO2 even with a full battery. The order of magnitude holds.

To check that it holds, I took a real car. The 195 hp Peugeot 308 Plug-in Hybrid (PHEV) shows a CO2 figure of 54 g/km in 2026, for 85 km of announced electric range and a 17.2 kWh gross battery (autotijd.be spec sheet, read on 14 October 2026). Using the empty-battery consumption Peugeot homologated on the 180 version, 6.2 l/100 km or about 143 g/km, the formula gives 17.7 g/km with the old curve, 56.2 g/km with Euro 6e-bis and 86.1 g/km with the 2027 curve.

Two grams away from the published figure on the second line. The calculation lands on its feet. In real use, its drivers log 4.15 l/100 km across 44 cars (Spritmonitor, 29 September 2026, a thin sample), and Peugeot covers the traction battery for 8 years or 160,000 km at 70 % of its capacity.

The table is harsh on small batteries. A plug-in hybrid with 40 km of range used to be counted two-thirds electric; with the 2027 curve it is counted one-fifth electric. Conversely, the more range a car has, the better it resists, which explains the race towards batteries of 20 kWh and more on new models.

Why did Europe tighten the calculation?

Because the old figure described a driver who barely exists. Since 2021, every new car carries a fuel and energy consumption meter whose data goes to the European Environment Agency. For plug-in hybrids registered in 2023, Transport & Environment calculated in October 2025 a real electric share of 27 %, while the old curve assumed 84 %.

Even after the second step, the curve will still assume about 36 % according to the same analysis, and real CO2 will remain roughly 18 % above the official figure. The correction is partial.

And it is still contested. Carmakers want the 2027 step cancelled. In mid-October 2026, that step is still in the timetable; the CO2 standards file was discussed at the Council on 12 October. I would not bet on the outcome, and I would not base a purchase on it.

The Belgian threshold moved from 50 to 75 g/km

This is the most direct Belgian consequence, and the one buyers know least. Since 2018, federal taxation has separated the genuine plug-in hybrid from the "fake hybrid": a PHEV whose battery offers less than 0.5 kWh per 100 kg of mass, or which emits more than 50 g/km. A fake hybrid is not taxed on its own CO2 but on that of the equivalent petrol or diesel version. If there is no equivalent, its CO2 is multiplied by 2.5.

With Euro 6e-bis, a compact plug-in hybrid would mechanically have crossed 50 g/km. Lawmakers therefore raised the threshold to 75 g/km for cars approved under Euro 6e-bis or a later standard, effective 1 January 2025, as Attentia summarised in September 2025. Cars still under the old calculation keep the 50 g/km threshold.

My table can be read backwards to find the threshold. For a plug-in hybrid at 140 g/km on an empty battery, you need:

• 21 km of range to stay under 75 g/km with the old curve;
• 56 km with Euro 6e-bis;
• 107 km with the 2027 curve;
• and 185 km to get back under 50 g/km with that same curve.

The plug-in 308 passes easily today: 54 g/km, and 1.05 kWh per 100 kg if you divide its 17.2 kWh gross by its 1,635 kg kerb weight. Approved under the 2027 curve with the same battery, it would end up around 86 g/km, so a fake hybrid under Belgian tax rules. A car identical down to the last bolt would switch regime depending on the month it was registered.

How much does a fake hybrid cost in benefit in kind?

This is where the difference is paid. In 2026, the benefit in kind (BIK) of a company car is calculated on 6/7 of the list price, multiplied by a percentage of 5.5 % adjusted by 0.1 point per gram above or below 70 g/km for petrol, with a 4 % floor, an 18 % cap and a minimum of 1,690 euros a year (BDO, 29 April 2026).

I took a new petrol plug-in hybrid with a list price of 40,000 euros, age coefficient at 100 %.

Calculations made on 14 October 2026. The BIK is added to the employee's taxable income: it is not paid euro for euro, it is taxed at the marginal rate. If an equivalent petrol version exists, its CO2 is used, and the gap is smaller than on the last line; the list published by the FPS Finance is only indicative, as the circular itself says.

Look at the step between the third and fourth lines. Twelve more grams, and the BIK triples. I dislike tax rules built on thresholds, they punish nearly identical cars. This one is a fine example.

For the employer, the question is settled differently: for a company, a plug-in hybrid acquired since 1 January 2026 is no longer deductible, genuine or fake. For a self-employed person under personal income tax, Attentia describes a 75 % regime until the end of 2027. The conditions depend on your situation: have your accountant confirm them before signing.

Wallonia, Brussels, Flanders: the regional effect stays small

Regional taxes barely react, because plug-in hybrids start from very low figures. I took the parameters of the Kia Niro plug-in hybrid (77 kW combustion engine, 1,993 kg maximum mass) with the 308's three CO2 levels.

In Wallonia, CO2 has been part of the formula since 1 July 2025, divided by 136 and multiplied by the base amount, the mass and the 0.8 hybrid coefficient (SPW Finances). Flanders raises CO2 to the power of six, which flattens everything below roughly 85 g/km. Brussels and the Walloon annual tax only look at the combustion engine's power and displacement: Euro 6e-bis changes nothing there. In Flanders, the annual tax is adjusted for CO2 relative to 149 g/km, so a plug-in hybrid's advantage there shrinks a little without disappearing.

The full scales are in the calculation of the registration tax on a hybrid car.

Before signing for a new plug-in hybrid, these are the lines I would have written into the offer:

• the exact approval standard (Euro 6e-bis or Euro 6e-bis-FCM) and the CO2 on the certificate of conformity for the version ordered, wheels included;
• the planned delivery date: a car ordered at the end of 2027 and registered in 2028 falls under the second step;
• the battery's gross capacity and the car's mass, to check the 0.5 kWh per 100 kg threshold;
• for a company car, the classification used by the fleet manager, genuine or fake hybrid, in writing.

If you are still unsure about the architecture itself, the selection method places your use in the right box, and the ranking of hybrids sold in Belgium gives range, logged consumption and battery warranty for each model. A plug-in hybrid with 40 km of range ordered today as a company car: I would not sign for it without seeing the BIK calculation in black and white.