WLTP car consumption: how to compare figures without drawing the wrong conclusions
A guide to understanding which WLTP figure to compare, how to interpret a range, and which version details can change official consumption and emissions.
Key points
WLTP consumption is a useful reference for comparing cars when the same indicator, test cycle and equivalent configurations are matched. It does not precisely predict each driver's costs, but it helps identify official differences between versions and build consistent cost scenarios.
Quick answer: compare the same WLTP figure and the same configuration
The WLTP figure allows new vehicles to be compared because it comes from a harmonised European Union protocol. For a nearly new car, use it only if you can identify its approved version and configuration in the original documentation.
Do not treat that figure as a promise that the car will use exactly the same amount on every journey. It is a laboratory result designed to make comparison repeatable, not an individual prediction. Before deciding between two versions, also check vehicle specifications, optional equipment and documented road-load characteristics such as mass, aerodynamic drag and tyre rolling resistance, even when the body style and model name appear identical.
If one specification sheet shows a WLTP figure and another shows data from an earlier cycle, the direct comparison does not work. The European Commission states that WLTP values will in many cases be higher than NEDC values for the same car.
Section references: Recomendación (UE) 2017/948 sobre comunicación de consumo y CO₂ WLTP ↗
- For an initial shortlist, compare the combined WLTP consumption of both versions.
- Check that both figures use the same approval test cycle.
- Note the vehicle specifications, optional equipment and relevant road-load characteristics.
- If any of those details are missing, treat the comparison as provisional and request the specification sheet or certificate of conformity for the specific vehicle.
What WLTP shows on a European specification sheet
WLTP is the test framework used to obtain approved fuel-consumption and CO₂-emissions values. The test is carried out in a laboratory, on a chassis dynamometer, under defined conditions and settings. Its value lies in providing a common basis for comparing vehicles, not in reproducing every possible road situation.
The European Commission Recommendation says that official fuel-consumption and CO₂ information should include at least the combined value. This makes it the most practical reference when you need to rank several candidates quickly. A specification sheet may also break down the result into low, medium, high and extra-high phases, as well as the combined value.
For a plug-in hybrid, you may also see a figure called “weighted, combined”. Do not automatically substitute it for the combined figure of a non-plug-in car: first identify exactly which indicator is published on each sheet. Comparing labels with different names can lead to a conclusion the figures do not support.
Section references: Recomendación (UE) 2017/948 sobre comunicación de consumo y CO₂ WLTP ↗ · Informe de verificación en servicio de CO₂ y consumo de vehículos ligeros ↗
- “Combined”: a consistent reference for a quick comparison between WLTP specification sheets.
- “Low”, “medium”, “high” and “extra high”: breakdowns by test-cycle phase; they show how the result changes within the test itself.
- “Weighted, combined”: an indicator that may appear for plug-in hybrids; it must be explicitly identified before being used against another figure.
Why two apparently identical cars can have different approved figures
An official difference does not, by itself, prove that one engine is inherently more efficient than another. The WLTP procedure takes into account specifications and optional equipment that affect the fuel consumption and CO₂ of each individual vehicle. As a result, two cars from the same range can have different figures.
To make sure configurations are comparable, check vehicle specifications and optional equipment. Then look at the elements that affect road load. The legislation highlights mass, aerodynamic resistance and tyre rolling resistance as relevant characteristics. Among other data, it also records test mass, mass in running order, tyre pressure and rolling resistance, and road-load coefficients.
Tyre pressure is among the technical data recorded in WLTP documentation. You should not assume that the advertised consumption of an entry-level version remains unchanged when another is configured with different equipment. The configurator should show how specific options alter official values.
Section references: Recomendación (UE) 2017/948 sobre comunicación de consumo y CO₂ WLTP ↗ · Reglamento (UE) 2017/1151, texto consolidado ↗ · Reglamento (UE) 2018/1832: interpolación, masa, aerodinámica y neumáticos ↗
- Compare the published specifications and optional equipment of each car.
- Check wheel and tyre sizes, as well as the options fitted to each car.
- Consider documented road-load characteristics, including mass, aerodynamic resistance and tyre rolling resistance.
- Distinguish between a base-version figure and the figure for the configured or display vehicle.
- If you are comparing a nearly new car, ask for the documentation for the registered version instead of relying only on a generic advert.
How to interpret a WLTP range without choosing the wrong end
It is common to find a consumption or CO₂ range rather than a single value. That range may group vehicles available with different configurations. The European Commission Recommendation says that the best and worst ends should reflect values for new cars available on the market and recorded in their certificates of conformity, but the range alone does not identify which specific combination corresponds to each end.
The practical conclusion is that the best value in a range should not automatically be assigned to the car you are configuring or the nearly new car you are considering. Find the figure for the complete configuration, including vehicle specifications, wheels and optional equipment. If the configurator does not make this clear, ask the seller for the documentation corresponding to the vehicle.
This step matters especially when the difference between candidates is small. If one version's range includes the other's value, there is not enough basis to decide using the advertised minimum alone. In that case, compare the specific values of both vehicles or keep the decision open until you have them.
| What to check | How to check it | Mistake it avoids |
|---|---|---|
| Published indicator | Compare combined with combined; identify weighted, combined separately. | Comparing figures that relate to different indicators. |
| Test cycle | Confirm that both values are WLTP. | Mixing a WLTP figure with an NEDC figure. |
| Vehicle specifications | Note the published specifications and optional equipment of each car. | Attributing a difference to the brand or engine without comparing equivalent configurations. |
| Configuration | Check the wheels, tyres and optional equipment of the vehicle or configurator. | Applying the best end of a generic range to your car. |
| Published range | Request the value for the specific configuration if only a range appears. | Assuming that every vehicle achieves the advertised minimum. |
Section references: Recomendación (UE) 2017/948 sobre comunicación de consumo y CO₂ WLTP ↗
- Read the range as the limits of several marketed configurations, not as the exact figure for every vehicle.
- Find the value linked to the final configuration before signing or reserving.
- Keep a screenshot or copy of the specification sheet consulted, including the date and configuration.
- Do not compare the low end of one range with the high end of another as though they were equivalent versions.
WLTP does not replace your everyday consumption
The WLTP test controls conditions in order to obtain comparable results. Everyday driving does not. The European Commission states that a laboratory test cannot cover every real-world situation and that there will always be some difference between laboratory measurement and real driving.
You do not need to turn the approved figure into a personal estimate for it to be useful. Use it to compare two cars under the same documented conditions; analyse your own usage separately. Ambient temperature, humidity, wind and driving style can significantly influence road results. These conditions may differ from those in the laboratory.
A common misreading is to conclude that a car “fails to comply” because it does not always reproduce the specification-sheet value. That is not what the figure is for. The correct reading is this: using the same WLTP metric and equivalent configurations, an official difference is a comparison criterion; a driver's real-world consumption will depend on conditions of use.
Section references: Informe de verificación en servicio de CO₂ y consumo de vehículos ligeros ↗ · Preguntas frecuentes sobre homologación de vehículos y WLTP ↗
- Separate two questions: “Which has the lower official figure?” and “How much fuel or energy will I use?”
- Do not rule out a model simply because someone else's consumption experience does not match the approval figure.
- Treat your type of journey, climate and driving style as your own variables, not as an official correction to the specification sheet.
From WLTP consumption to a cost scenario: use it as an assumption
Once you have chosen the comparable figure, you can carry out an indicative calculation for a financial scenario. For two cars using the same energy source and whose specification sheets express consumption in the same unit, multiply WLTP consumption by the planned distance and by the unit price you want to analyse. If consumption is expressed per 100 kilometres, first divide annual kilometres by 100.
The result is not an exact forecast of your bill: it is a scenario based on approved consumption and an energy price chosen by you. Its value is that it lets you apply the same distance and price to every candidate. You can calculate a cautious scenario by varying the price, but without replacing the WLTP figure with an assumed personal real-world figure.
To organise the purchase properly, keep the link or document for the specification sheet, the consultation date, the configuration and the energy price used alongside each result. This allows you to update the scenario if a wheel, optional extra, available version or price changes. The energy tool can help you organise this calculation.
Section references: Recomendación (UE) 2017/948 sobre comunicación de consumo y CO₂ WLTP ↗ · Preguntas frecuentes sobre homologación de vehículos y WLTP ↗
- Set the same annual distance for every car being compared.
- Apply the same price per unit of energy when the energy source and unit are equivalent.
- Do not mix consumption figures expressed in different units in the same calculation.
- Label the result as a “WLTP scenario”, not as a guaranteed cost.
- Recalculate if the final configuration differs from the one that produced the initial figure.
Which WLTP consumption figure should I compare first?
Combined WLTP consumption is the most consistent starting point for a quick comparison, provided both specification sheets refer to equivalent versions and configurations.
Can I compare NEDC and WLTP directly?
Not directly. They are different test cycles, and the European Commission states that WLTP values will in many cases be higher than NEDC values for the same car.
Why does the same model have a WLTP consumption range?
Because the range may cover different available configurations. Vehicle specifications and optional equipment can affect approved values, including relevant road-load characteristics such as mass, aerodynamic drag and tyre rolling resistance.
Will the WLTP value be my real-world consumption?
Not necessarily. It is a laboratory measurement for comparing vehicles; real conditions such as weather, wind and driving style can produce different results.
How do I use WLTP to estimate annual costs?
Apply the approved consumption to the same annual distance and a defined energy price for all equivalent candidates. Interpret the result as a comparison scenario, not as a guaranteed cost.
