The Wall Street Journal Asia weekend edition reviewed the Porsche Cayenne S Hybrid, proclaiming “Porsche takes a big step into being green.” Just how big a step is that?
The Cayenne is a top-of-the line SUV which would normally be called a gas guzzler/emblem of conspicuous consumption. By using hybrid technology in the engine and adding electronic controls to cut fuel drain, the Cayenne hybrid achieves a 25-30% improvement in fuel economy, or around 23/26 MPG city/highway (9-10 litres per 100 km). Porsche also boasts that the Cayenne hybrid reduces CO2 emissions to “just 193 g/km”. This is significant, given that any other car with an engine larger than 4 litres will normally emit well over 200 and sometimes 300 g/km CO2. These figures appear to be significant improvements indeed.
But, before you run out to buy the car in order to brush up your green credentials, do consider several factors which are conveniently disregarded in the WSJ write-up.
First, the environmental impacts of a vehicle include not just the fuel economy and CO2 emissions while operating, but the CO2 emissions and resources consumed in production. The auto industry largely reports only on the CO2 emissions from their own facilities, but given that most auto parts have been outsourced to third party suppliers, it’s clear that a lot is excluded a priori. Even under these conditions, the CO2 emitted in the auto brand’s own facilities is estimated to account for 15-20% of the auto’s total CO2 emissions over a life of 15 years. The Cayenne Hybrid is five tons of steel –even a rough counting of the emissions from components and manufacturing come to much higher than just 20%.
Second, while the hybrid model emissions are an improvement upon the baseline 6-litre model, 193 g/km CO2 is still very high. The EU is considering legislation which would put a cap on CO2 emissions of just 120 g/km for the majority of passenger vehicles. Non-hybrid sedans emit between 100 and 150 g/km. Automakers argue that larger vehicles deserve a higher cap, which may be true when applied to buses and vans, but in the consumer segment, there are good reasons why choosing an SUV (over a sedan) is not a necessity, but rather an environmentally poor choice which should bear costs.
The US is the largest SUV market in the world, and it’s no surprise that US autos emit an average of 255 g/km CO2, compared to 130.8 g/km for Japan and 140 g/km for Europe. Bringing these numbers down significantly requires that people steer clear of environmentally bad choices like SUVs, rather than looking to make marginal improvements on bad choices. But this would be bad for Porsche, so they just don’t mention it. Indeed, any company that benefits from an economy in which rising consumption is good and in which happiness is defined in terms of possessions, would lose if it told consumers the truth about their choices.
Thus, we are subject to a constant stream of misinformation that peddles a fundamentally unsustainable product as something clean and green. Don’t buy it.

