The dirty Australian loophole in plug-in hybrid emissions ratings

We have a problem in Australia with testing the CO2 emissions of plug-in hybrids (PHEVs). I have had an interest in this topic for some time, but the more I’ve followed what is happening in the European Union (EU), the more worrisome the Australian situation becomes.

It’s fairly well understood that the emissions from PHEVs are highly dependent on the behaviour of the driver – much more than for a conventional combustion engine vehicle, or indeed an EV.

Just because you have charge in your battery doesn’t guarantee the combustion engine won’t start under load. To really get an environmental and financial benefit from a PHEV, the driver must charge the battery scrupulously after almost every trip to minimise fuel use.

Thinking that buying a PHEV is going to automatically slash your tailpipe pollution is like thinking that buying a gym membership is automatically going to make you fit. You actually need to be committed to doing some work.

Australia currently tests vehicles for CO2 emissions using the New European Driving Cycle (NEDC). The NEDC test for PHEVs was devised before there was any significant experience with these vehicles.

The NEDC simply assumes that every driver operates their PHEV the same way: deplete a battery from fully charged, drive it a further 25 kilometres using fuel, and then plug it in to re-charge.

If you have a driver who rarely plugs it in, the real-world emissions of the vehicle are much higher. Even a diligent ‘plugger’ will have much higher emissions if they do even a few long-distance trips. The NEDC model is simple but it’s clearly flawed.

With the introduction of the New Vehicle Efficiency Standard (NVES), Australia is moving over time to the Worldwide Harmonized Light Vehicles Test Procedure (WLTP). This improves the procedure for testing PHEV emissions by applying so-called utility factor curves.

These curves specify, for a given electric range, the fraction of electric operation. The logic goes that the larger the battery, the greater the proportion of time the vehicle will spend in electric operation, until a point. Three utility factor curves are shown in the following figure and will be referred back to later. The red curve is the one that is applied in Australia today.

Source: J. Dornoff/ICCT (2022), “Euro 6e: Changes to the European Union light-duty vehicle type-approval procedure”

Every new vehicle sold in the European Union from 2020 must be equipped with on-board fuel consumption monitoring and the data collected over-the-air or when vehicles are serviced. Data are now available for 2021, 2022 and 2023. The European Environment Agency has been able to determine the gap between the rated and actual emissions of PHEVs as follows:

Source: European Environment Agency, “Real world CO2 emissions from new vans and cars”

You may ask, how can this percentage gap be getting wider? Aren’t the batteries in newer PHEV models entering the fleet in 2022 and 2023 larger, allowing drivers to travel further on electricity and less frequently using the combustion engine?

The answer is that while newer PHEV models do have larger batteries, this gives them an even more optimistic emissions rating than before. They also achieve poorer economy when driving on fuel due to the increased battery weight. If a vehicle is still not plugged in regularly, then this gap becomes wider.

Recognising this unacceptable situation, the European Commission commenced an interim regulation in January this year called  Euro 6e-bis. This regulation improves the accuracy of PHEV emissions testing by adjusting the utility factor curve (see tan curve in the chart).

In 2027, another revision of the regulation (Euro 6e-bis-FCM) will come into force which further improves the emissions ratings to reflect the actual fuel consumption data (see cyan curve in the chart). For a PHEV with 100 km of electric range, the original (red) utility factor curve from Euro 6d assumed about 90% electric operation.

With the 2027 regulation, that same vehicle will be assumed to have a bit over 40% electric operation. That may seem low but one long trip mostly using fuel cancels out many weeks of purely electric local driving. The 2027 standard is expected to produce values acceptably close to real-world emissions, but may still be amended in future.

The effect of these changes is substantial. In an International Council on Clean Transportation policy brief, the CO2 emissions rating for a popular plug-in hybrid with 70 km of electric range was re-calculated using the Euro 6e-bis and 6e-bis-FCM regulations.

Its rating increased from an initial 45 g/km by the Euro 6d standard to 96 g/km (Euro 6e-bis) and up to 122 g/km by the most realistic Euro 6e-bis-FCM standard.

That’s nearly three times higher than the original rating and comparable to many non-pluggable hybrids on the market. Given this new rating, if you want a low emissions vehicle, you will need to buy a proper battery EV.

If we don’t have realistic ratings for plug-in hybrids, they will undermine the integrity of the NVES by allowing importers to claim spurious credits for PHEVs sold with artificially low CO2 emissions ratings while, in practice, they will pollute much more.

This will become the next failure among several in emissions accounting. Consumers will also be misled by the advertised fuel consumption figures that are so low they are rarely achieved in practice. Vehicles often fall a little short of the fuel economy shown on the windscreen sticker, but these discrepancies are next level.

The EU is acting decisively to remedy this flaw in PHEV emissions testing and so must Australia. The Australian Government, having spent a couple of years in the trenches over NVES, is being slow to react to this problem and needs to swiftly adopt the improved test procedure for plug-in hybrids.

Ben Elliston is the chair of the ACT branch of the Australian Electric Vehicle Association (AEVA). Opinions expressed in this article are his own and not necessarily those of AEVA.

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