According to the US Environmental Protection Agency (EPA), one litre of petrol contains exactly 8.9 kWh of thermal energy. When you pump a litre of petrol into a traditional internal combustion engine (ICE) car, where does it go?
To test it out, we drove variants of the same car – Kia’s Carens Clavis (Rs 11.21-21.56 lakh) and the Carens Clavis EV (Rs 17.99-24.99 lakh).
In our tests, the Carens Clavis petrol returned 12-14 km/litre in city traffic. The rest of the energy – physics tells you it’s 70-75% – was lost to the atmosphere as wasted heat, sound, and friction.
In the electric version of the Carens Clavis, the math became mind-bending.
Driving it in peak Bengaluru traffic – where frequent braking regenerates energy – the Clavis EV covered almost 10 km on one kWh of electricity. This means that on 8.9 kWh – or one litre equivalent of petrol – it was able to travel a whopping 89 km/litre, a figure that petrol/diesel/CNG or even strong hybrid engines cannot match, ever. That’s how efficient electric cars are.
Why is ICE so wasteful?
It’s fundamental physics. Even after a century of R&D, the thermal efficiency of a regular ICE hasn’t gone beyond 25-30% – though there have been some outliers like Nissan’s e-Power with 50% efficiency – because ICE uses pistons, valves, cooling systems, and multispeed transmissions, and there is energy leak at every step. In addition, every second spent idling at a traffic light burns fuel.
On the other hand, electric motors operate at an energy efficiency rate of almost 90%, because they have fewer parts and therefore less friction and less energy loss. In addition, EVs recapture kinetic energy to recharge the battery during deceleration or when going downhill – while driving the Clavis EV down from Nandi Hills, the battery percentage actually increased.
What about city traffic?
The stop-and-go traffic kills fuel efficiency, but is an asset for an EV. Whenever you lift your foot off the accelerator pedal, the direction of electricity and torque reverses, turning the motor into a generator, charging the battery.
The EV supply chain argument
A common critique of the electric transition is geopolitics: does shifting away from oil trade dependence on the Middle East for a reliance on China’s control of rare-earth mineral processing?
While it’s a valid concern, there is a difference in the way these resources are used.
When you burn one litre of petrol to travel 12 km in an ICE car, that energy is gone forever.
But a battery is a recyclable container. At the end of an EV’s road life, modern recycling systems can recover up to 90% of the core materials (lithium, cobalt, nickel) to manufacture a brand-new battery.
EV versus ICE
Finally, choosing between and EV and ICE depends on a lot of things – including charging infrastructure, range, electricity supply, where you live, how you drive, resale value, budget – but physics has proven that if ICE simply burns resources (it’s combustion, after all), EV conserves them.
