NGC Rating

NGC Rating

The NGC Rating expresses a vehicle's environmental impact as a score ranging from 0 for the greenest vehicles to 100+ for the most polluting. Next Green Car's database includes Ratings for over 50,000 UK models registered since 2001. Ratings are available for petrol, diesel, hybrid, electric, biofuel, LPG and natural gas vehicles.

What is the Next Green Car Rating?

The NGC Rating assesses a vehicle's environmental impact over its whole life cycle – including vehicle use, fuel production and vehicle manufacture.

The Rating is designed to be easy-to-use and is expressed as a score out of 100 ranging from 0 for the greenest vehicles to 100+ for the most polluting.

The NGC Rating was developed by Next Green Car and is a unique method of assessing the environmental impact of a vehicle.

What is life cycle analysis?

The Next Green Car Rating is based on an assessment of the life cycle emissions – not just those from the exhaust or 'tailpipe'.

As well as the tailpipe emissions produced during a vehicle's use, life cycle emissions include 'upstream' pollutants produced during fuel production (including primary production, extraction, transportation, and refining) and vehicle production (manufacture and assembly).

Lifecycle schematic diagram

Why use the Next Green Car Rating?

1. The NGC Rating includes all measured air-based emissions – not just CO2

This allows a realistic comparison between different vehicle and fuel types – for example, while diesel typically has lower tailpipe CO2 emissions than petrol, diesel emissions include higher levels of NOx and particulates.

The emissions assessed are: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), carbon monoxide (CO), oxides of nitrogen (NOx), hydrocarbons (HCs), particulates (PM), and sulphur dioxide (SO2).

2. The NGC Rating includes life cycle emissions, not just tailpipe emission.

This enables a fair comparison of all conventional and alternative vehicle types – for example, hybrids offer better fuel economy, but also have higher manufacturing emissions.

It also means that zero-emission vehicles can be fairly assessed – while electric cars have zero tailpipe CO2, the NGC ratings take into account the emissions produced by electricity-generation and vehicles manufacture.

3. The NGC Rating is an impact assessment, not just an emissions inventory

Rather than just quantify the amount of each of the eight emissions, the NGC Rating assesses by the environmental impact of the emissions.

Not only does this more accurately account for the impacts and location of different emissions, using the total environmental impact makes a comparison of eight emissions possible.

4. The NGC Rating provides an easy-to-understand system for consumers

The NGC Rating is designed to used by non-experts and is therefore expressed as a score out of 100 ranging from 0 for the greenest vehicles to 100+ for the most polluting.

How is the Next Green Car Rating calculated?

The NGC Rating is based on an assessment of the environmental impacts associated with a car's use and manufacture. This includes all aspects of producing and using the fuel - the fuel cycle (primary production, extraction, transportation, refining, and vehicle operation), as well as the vehicle's manufacture, assembly and disposal - the vehicle cycle.

The NGC Rating analysis first quantifies the extent of life cycle air emissions arising from the fuel and vehicle cycles (known as an emissions inventory). The air emissions assessed include the so-called 'regulated emissions' - carbon monoxide (CO), oxides of nitrogen (NOx), non-methane organic gases (NMOG) and particulates (PM) - and sulphur dioxide (SO2). In addition, the three main greenhouse gases associated with road transport are assessed: carbon dioxide (CO2) , nitrous oxide (N2O) and methane (CH4).

The analysis then conducts an emissions impact assessment - as its name suggests, this quantifies the impacts of the emissions rather than just quantifying the amount of emissions produced. The advantage of this approach is that the varying levels of all the emissions assessed can be combined to produce an overall environmental impact - without this approach it is difficult to know how to compare (for example) a car with high CO2 and low NOx, with a second vehicle that has low CO2 and high NOx.

The emissions impact assessment is achieved by the use of an environmental rating tool first developed by the European Cleaner Drive Programme to assess the impacts associated with the fuel cycle. This rating system uses recognized 'external costs' to establish the relative weight to attach to different emissions - the external costs are values expressed in monetary terms that reflect the overall damage to the environment and to human health. The analysis used by Next Green Car extends the Cleaner Drive method to include vehicle cycle (car manufacture and assembly).

Using the NGC Rating system, the level of environmental impacts are expressed as a score between 0-100 - the lower the score, the less the environmental impact (this reverses the Cleaner Drive scores which were higher for lower emission vehicles).

Input data for the NGC Rating methodology comes from number of reference sources including: the Vehicle Certification Agency (for vehicle or tailpipe emissions), and several academic papers that estimate the emissions produced during the production of materials used for vehicle manufacture.

For more details of the methodology used to calculate the NGC Rating, download the PDF document: NGC Rating 2.1 Methodology (United Kingdom) 2016

Ben Lane

Author:Ben Lane
Date Updated:10th Mar 2015

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