hybridmetrics

Fact sheet · updated

WHAT THE FIGURES MEAN

Read the
hybrid numbers.

Hybrid is one word for three quite different cars.

Check a hybrid type
An unbadged compact family car parked on a brick driveway at dusk, plugged into a wall-mounted home charger
AI-generated image, not a photograph of a real person or place.

CHARGEit often

Some cannot move on electricity at all, some can creep along quietly in town, and some can be plugged in and driven for miles on battery. Their official figures come from a laboratory test, and real-world data shows the gap is largest for plug-ins that are not charged often.

At a glance

19% more

Real-world CO2 above official, 2023

For combustion-engine cars, including mild and full hybrids, real-world emissions exceeded the official values by 19% in 2023, up from 18% in 2021.

PETROL, DIESEL AND HYBRIDS · ICCT 2026

≈ 5× official

Real-world CO2 above official, 2023

Plug-in hybrids emitted 401% more than their official figures, about five times as much. The ICCT says this mainly comes from the test overestimating how much they are driven on electricity.

PLUG-IN HYBRIDS · ICCT 2026

TWO NUMBERS WORTH KNOWING

Official figures
versus the road.

From fuel meters fitted in about 8 million new cars
registered in Europe between 2021 and 2023.

Source: ICCT, On the way to real-world CO2 values? Evidence from 2021–2023 on-board fuel consumption monitoring data (June 2026). Figures are fleet averages, not any one car.

A QUICK TYPE CHECK

How much can it
drive on battery?

Pick a kind of hybrid, or how a plug-in is used, to see how much driving it can do on electricity alone. The bar shows the electric share compared with the other choices.

General descriptions of each type. Individual models differ, so check the figures for the car you are looking at.

Hybrid type check

Choose a type
Mild hybridNo electric-only driving

A battery and motor help power the car and let the engine switch off when stopped, for example at traffic lights. It cannot drive on electricity alone.

Full hybridShort, low-speed trips

A larger battery and more powerful motor can drive the car for short distances at low speeds. It still cannot be plugged in: the engine and braking recharge it.

Plug-in, charged between trips≈ 15 to 60+ miles

The electric range of current models. Driven less than that range and charged between trips, it may be possible to use only electric power.

Plug-in, never chargedLike a similar hybrid

If it is never plugged in, the US Department of Energy says its fuel economy will be about the same as a similarly sized ordinary hybrid.

Source: US Department of Energy, Alternative Fuels Data Center pages on hybrid and plug-in hybrid electric vehicles.

THE SHORT ANSWER

Three kinds
of hybrid.

The bigger the battery, the more electric driving it can do.
Only a plug-in can be charged from the mains.

MILD AND FULL

Hybrids that charge themselves

A mild hybrid's motor helps the engine but cannot drive the car on electricity alone. A full hybrid has a bigger battery and motor and can drive short distances at low speeds.

Compare the types

PLUG-IN

A bigger battery you charge

A plug-in hybrid can be charged from the mains. US Department of Energy figures give current models an electric range of about 15 to 60-plus miles.

Get the most from it

OFFICIAL FIGURES

A lab test, for comparing cars

Official fuel and CO2 figures come from the WLTP laboratory test. The UK Vehicle Certification Agency says they are a way of comparing similar models, not a promise of what you will get.

See the real-world gap
A small car driving slowly along a quiet tree-lined town street in soft morning light
AI-generated image, not a photograph of a real person or place.

FOUR WAYS TO READ THEM

Fair comparisons,
fewer surprises.

These are not tips for buying any particular car. They are about understanding what the figures you see actually describe.

  1. Check which kind of hybrid it is

    Mild, full and plug-in hybrids work very differently. Only a full or plug-in hybrid can drive on electricity alone, and only a plug-in can be charged from the mains.

  2. Compare like with like

    The VCA says WLTP figures are obtained under specific test conditions and serve as a means of comparing models of a similar type.

  3. Expect your own figure to differ

    Driving style, accessories and extra weight all change the fuel you actually use, the VCA notes. Real-world data shows ordinary cars averaging around a fifth above their official figures.

  4. Plug a plug-in in

    Consistent charging is the best way to get the electric benefits, says the US Department of Energy. Never charged, a plug-in uses about as much fuel as a similar ordinary hybrid.

WHY PLUG-INS SHOW THE BIGGEST GAP

It depends how
often you charge.

A plug-in's official figure blends battery driving and engine driving using a 'utility factor', an assumption about how much distance is electric. Data from about one million plug-ins in Europe found only around a quarter of the distance was driven electrically (27–31%), and average real-world use was 5.9 litres per 100 km.

Even with the battery in use the engine ran a fair amount: about 2.8 l/100 km on average, rising to 7.4 l/100 km once the battery was depleted. EU rules are being tightened in steps; the researchers estimate the gap falls from over 300% under the pre-2025 rules to about 40% under the version due from 2027.

A hand plugging a charging connector into the charge port on the side of a car
AI-generated image, not a photograph of a real person or place.

Questions

Questions people ask

What is the difference between a mild and a full hybrid?

A mild hybrid's battery and motor help the engine and let it switch off when stopped, but cannot drive the car on electricity alone. A full hybrid has a bigger battery and motor and can drive short distances at low speeds on electricity.

Do you have to plug in a hybrid?

Only plug-in hybrids can be charged from the mains. Mild and full hybrids are charged by the engine and by regenerative braking, which turns the motor into a generator when the car slows down.

How far can a plug-in hybrid go on electricity?

The US Department of Energy gives current models an electric range of about 15 to 60-plus miles. Check the figure for the specific model you are looking at.

What does WLTP mean?

The Worldwide Harmonised Light Vehicle Test Procedure. It replaced the older NEDC test for new cars from September 2017 and is run in a laboratory, with results reported as Low, Medium, High, Extra-high and Combined.

Why is my real-world fuel use higher than the official figure?

The official figure comes from a lab test under set conditions. In 2023, European cars with combustion engines used around 19% more than official in real driving, and plug-in hybrids about five times more, mostly because they were charged less than the test assumes.

Sources

Where the facts come from

  1. US Department of Energy, Alternative Fuels Data Center: Hybrid Electric Vehicles
  2. US Department of Energy, Alternative Fuels Data Center: Plug-In Hybrid Electric Vehicles
  3. Vehicle Certification Agency: The Worldwide Harmonised Light Vehicle Test Procedure (WLTP)
  4. ICCT (2026): On the way to real-world CO2 values? Evidence from 2021–2023 OBFCM data in the European passenger car market
  5. Plötz et al., Fraunhofer ISI and Öko-Institut: Regulatory adjustments needed for plug-in hybrid vehicles in Europe (policy brief)

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