Thread by @DrSimEvans

This widely-shared chart @VWGroup compares lifecycle emissions from a Golf Diesel with the e-Golf EV.

It shows the EV only starts saving CO2 after ~120,000km

But correcting for questionable assumptions shows that should be *less than 25,000km*

THREAD

carbonbrief.org/factcheck-how-…

First of all I asked VW if it could provide more info on the assumptions in its analysis, which the press team kindly sent me, see pic attached.

(You can see more limited info on VW's website:

volkswagenag.com/en/news/storie… )

Then I reverse-engineered the original VW chart, based on the assumptions they shared and our earlier EV factcheck:

carbonbrief.org/factcheck-how-…

As per the VW chart, this shows the e-Golf EV is better for the climate only after around 120,000km.

But looking at the VW assumptions, several of them are pretty questionable.

(VW tells me it is in the process of updating its analysis in the coming months…)

Meanwhile, what happens if we correct its numbers?

First, we know that real-world tailpipe emissions are much higher than the official "test cycle" CO2 & fuel efficiency figures reported by manufacturers.

@TheICCT analysis suggests +35% for a VW Golf

(figure 10 / page 14)

theicct.org/sites/default/…

Second, VW's analysis appears to be assuming battery production emissions of 156kgCO2e/kWh.

Our literature review suggests a top-end of more like 100kg.

carbonbrief.org/factcheck-how-…

Third, the EU average electricity mix is already much cleaner – at 265gCO2/kWh in 2019 – than the 375gCO2 figure implied by VW's assumptions

carbonbrief.org/factcheck-how-…

(I know, marginal intensity, don't @ me. But I've assumed constant intensity, whereas in reality it'll improve)

Fourth, VW includes fuel cycle emissions – for oil refining, transport, etc – equivalent to 11% of tailpipe emissions.

But research suggests it should be more like 24%, for diesel:

https://twitter.com/AukeHoekstra/status/1229108140723011585

(In our factcheck we used ICCT figure of ~28%

carbonbrief.org/factcheck-how-… )

Taking all of these corrections together, the e-Golf EV has paid off its carbon debt within 25,000km.

Nearly 5x faster than the 120,000km reported by VW!

Across 200,000km, the EV has less than half the lifetime emissions of the Golf Diesel.

carbonbrief.org/factcheck-how-…

If the battery is produced using cleaner electricity, then the climate benefits of the EV are even greater, meaning it would beat the Golf diesel within 20,000km.

carbonbrief.org/factcheck-how-…

Finally, as you can see from the chart, even in a best case the EV still has significant lifecycle emissions (which are much lower than the diesel), though these will improve.

Walking, cycling, bus or train are likely to be even lower carbon than the EV.

carbonbrief.org/factcheck-how-…