Disclaimer

Rating of Plug-in Hybrid (PHEV) tests

A PHEV can be operated the following ways:

• CD (Charge Depleting) mode: with the high voltage (HV) battery charged where the vehicle will prioritise, if the situation allows it, to be run predominantly in electric vehicle (EV) mode only activating the internal combustion engine (ICE) in exceptional cases.
• CS (Charge Sustaining) mode: with the HV battery discharged where the vehicle acts like a NOVC-HEV (not off-vehicle charging (i.e. conventional) hybrid electric vehicle), running predominantly the ICE. The hybrid management system selects the strategy to be followed, i.e. when the power at the wheels is provided by the ICE, by the electric motor or both.

Green NCAP’s test matrix aims to provide consumption and emissions values that are more realistic than the figures stated in official documents. This is achieved by testing under more representative conditions and postprocessing the results in a more sensible way by weighing both modes in accordance to the measured useful electric range.

The tests for PHEVs consider the same test matrix as for conventional and hybrid vehicles when the vehicle is working in CS (Charge Sustaining) mode with the addition of the following tests done in CD (Charge Depleting) mode: WLTC+ CD Sequence (cold start laboratory test at 23°C ambient temperature), Winter cold start test, Real-world mixed drive and the Short City Trip. The WLTC+ CD Sequence consists of driving the vehicle over the WLTC+ test starting with the HV battery at 100% state of charge (SoC). The vehicle is driven over multiple WLTC+ tests in a row until it reaches the CS condition. This WLTC+ CD Sequence procedure is also used to determine the available battery capacity and the EAER (Equivalent All Electric Range). EAER stands for the total driving range attributable to the use of electricity from the battery over the WLTC+ CD Sequence.

For PHEV, each index scores are calculated in both CD and CS mode and combined. The contribution of results in each mode is determined by the obtained EAER. The higher the EAER, the lower the influence of the results in CS mode and the other way round, see Table 1.

Limitations

Clean Air Index

The Clean Air Index is comprised of scores for various stages of the car’s life. The pollutant emissions created when the car is produced are calculated using the different masses of materials used. Large, heavy cars perform worse in this part of the assessment as they make greater use of raw materials and processing. The analysis of the Usage phase of the car’s life considers many factors: the pollutants emitted at the tailpipe while driving; the pollutants produced in the upstream manufacture and distribution of the energy source (fuel or electricity); tyre and brake abrasion, and maintenance. Finally, the savings that can be made in the production of future vehicles by the recovery and re-use of materials from the car when it is destroyed are also accounted for. Each of these elements is scored separately and a weighting applied to account for their real-life impact on health. For example, tailpipe emissions are weighted heavily in the overall score as these are created very close to human habitation, often in cities, and have a severe impact on health. Emissions from production facilities are weighted less heavily as manufacturing plants are often remote, and the pollutants they emit mostly disperse before they impact human health.

Energy Efficiency Index

The Energy Efficiency Index also considers the various stages of the car’s life, and uses LCA to determine the energy consumed during production; during usage, as measured in Green NCAP’s tests but with a scaling factor to take account of the energy needed to produce that used by the car while driving; and the energy benefit occurring when materials are recovered and recycled at the car’s end-of-life.

Greenhouse Gas Index

As with the other two indexes, the Greenhouse Gas Index considers the whole vehicle life-cycle. However, unlike the pollutant emissions evaluated in the Clean Air Index, the harmful effects of which are largely local, greenhouse gases affect the entire planet so, for this index, the total emissions are summed before they are scored. In other words, greenhouse gases emitted from a remote manufacturing facility have just as much impact on global heating than those from a car’s tailpipe. For the usage phase, the upstream factors consider such things as the extraction from raw oil and usage of resources, the construction of refineries and renewable power plants, the supply and usage of resources needed for their operation etc.

Green NCAP looks at three of the most important greenhouse gases: Carbon Dioxide (CO₂), Nitrous Oxide (N₂O) and Methane (CH₄). Other gases emitted by the vehicle which may have a ‘greenhouse effect’ are not measured or estimated.

Starting with 2025, the LCA takes into account where production is done, as some parts of the world have higher industry emissions than others. A study performed for Green NCAP by A2MAC1, delivered the foundation for the estimation of these differences.

Laboratory Tests

For its laboratory tests, Green NCAP currently uses the same road load data used for legislative testing. 

Measurement Technology

Green NCAP’s test laboratories measure particulates with a 10 nm (nanometer) cut-off filter, which include the very injurious, super-tiny particles emitted in large numbers by some cars.