This is the estimate for a typical car-driver driving a typical car today.
Later chapters will discuss the average consumption of all the people in
Britain, taking into account the fact that not everyone drives. We’ll also
discuss in Part II what the consumption could be, with the help of other
technologies such as electric cars.
Why does the car deliver 33 miles per gallon? Where’s that energy
going? Could we manufacture cars that do 3300 miles per gallon? If we are
interested in trying to reduce cars’ consumption, we need to understand
the physics behind cars’ consumption. These questions are answered in
the accompanying technical chapter A (p254), which provides a cartoon
theory of cars’ consumption. I encourage you to read the technical chapters
if formulae like 1⁄2mv2 don’t give you medical problems.
Chapter 3’s conclusion: a typical car-driver uses about 40 kWh per day.
Next we need to get the sustainable-production stack going, so we have
something to compare this estimate with.
Good point. When I estimate the energy consumed by a particular
activity, I tend to choose a fairly tight “boundary” around the activity.
This choice makes the estimation easier, but I agree that it’s a good idea
to try to estimate the full energy impact of an activity. It’s been estimated
that making each unit of petrol requires an input of 1.4 units of oil and
other primary fuels (Treloar et al., 2004).
Yes, that cost fell outside the boundary of this calculation too. We’ll
talk about car-making in Chapter 15.
29 For the distance travelled per day, let’s use 50 km. This corresponds to
18 000 km (11 000 miles) per year. Roughly half of the British population
drive to work. The total amount of car travel in the UK is 686 billion
passenger-km per year, which corresponds to an “average distance travelled
by car per British person” of 30 km per day. Source: Department for Trans-
port [ ]. As I said on p22, I aim to estimate the consumption of a
“typical moderately-affluent person” – the consumption that many people
aspire to. Some people don’t drive much. In this chapter, I want to estimate
the energy consumed by someone who chooses to drive, rather than deper-
sonalize the answer by reporting the UK average, which mixes together the
drivers and non-drivers. If I said “the average use of energy for car driving