The REVA electric car was launched in June 2001 in Bangalore and is ex-

ported to the UK as the G-Wiz. The G-Wiz’s electric motor has a peak

power of 13 kW, and can produce a sustained power of 4.8 kW. The motor

provides regenerative braking. It is powered by eight 6-volt lead acid

batteries, which when fully charged give a range of “up to 77 km.” A full

charge consumes 9.7 kWh of electricity. These figures imply a transport

cost of 13 kWh per 100 km.

Manufacturers always quote the best possible performance of their

products. What happens in real life? The real-life performance of a G-Wiz

in London is shown in figure 20.21. Over the course of 19 recharges,

the average transport cost of this G-Wiz is 21 kWh per 100 km – about four

times better than an average fossil fuel car. The best result was 16 kWh

per 100 km, and the worst was 33 kWh per 100 km. If you are interested

in carbon emissions, 21 kWh per 100 km is equivalent to 105 g CO_{2} per km,

assuming that electricity has a footprint of 500 g CO_{2} per kWh.

Now, the G-Wiz sits at one end of the performance spectrum. What if

we demand more – more acceleration, more speed, and more range? At

the other end of the spectrum is the Tesla Roadster. The Tesla Roadster

2008 has a range of 220 miles (354 km); its lithium-ion battery pack stores

53 kWh and weighs 450 kg (120 Wh/kg). The vehicle weighs 1220 kg and

its motor’s maximum power is 185 kW. What is the energy-consumption

of this muscle car? Remarkably, it’s better than the G-Wiz: 15 kWh per

100 km. Evidence that a range of 354 km should be enough for most people

most of the time comes from the fact that only 8.3% of commuters travel

more than 30 km to their workplace.

I’ve looked up the performance figures for lots of electric vehicles –

they’re listed in this chapter’s end-notes – and they seem to be consistent

with this summary: electric vehicles can deliver transport at an energy cost

of roughly 15 kWh per 100 km. That’s five times better than our baseline

fossil-car, and significantly better than any hybrid cars. Hurray! To achieve

economical transport, we don’t have to huddle together in public transport

– we can still hurtle around, enjoying all the pleasures and freedoms of solo

travel, thanks to electric vehicles.