Does Scraping Old Cars Lead to Reduced Energy Use?

In the comment section of a previous post, reader Taurus ponders the effect of the car scraping bonus on overall energy use.

Here are my thoughts on this topic:

- The car scraping bonus subsidises 2 million new car purchases with a total amount of 5 bn €.

- Assume half of those new cars would have been bought anyway, whereas the other half was bought earlier than otherwise intended, reducing their useful life by 10 %.

- Assume the lifespan of a car is 150,000 km, i.e. a reduction by 10 % equals 15,000 km.

- Assume that the new cars consume 1l/100km less than the scraped old cars (my new Toyota replacing a 14 year old car of a similar category needs roughly 1l less).

- Assume that the energy needed to produce a new car is 23,000 KWh (based on calculations made by Volkswagen for a VW Golf).

How much fuel is saved by the scraping?

1 million cars * 15,000 km * 0.01 litres saved = 150 million litres of oil saved

How much energy is needed to build the new cars ahead of normal schedule?

1 million cars * 23,000 KWh * 10 % of lifespan = 2.3 bn KWh of additional energy used

Based on current prices, 150 million litres of oil cost roughly 50 million Euros on the world market. 2.3 bn KWh for industrial use cost around 200 million Euros.

=> Based on the assumptions I used, the scraping bonus leads to significantly more energy use, not less.

You can play around with the assumptions (e.g. the average car bought under the scraping bonus is smaller than a VW Golf and therefore needs less production energy; also, if people trade down to smaller cars, the savings on fuel consumption may be bigger), but I don't think you can come up with a realistic set of assumptions that implies significant net energy savings.