If you were thinking of swapping the Mercedes-Benz S-Class for a supermini to save the planet, think again. Downsizing is no longer enough when it comes to reducing CO2.

Small cars are harshly treated in this year’s stiff new EU emissions legislation and superminis are going to have to get electrified to keep up. Nor is a battery electric going to cut it: they’re too expensive. As Ali Kassai, director of Renault’s electric vehicle product planning, points out: “There’s a lot of resistance from buyers to the idea of a £30,000 battery electric hatchback.”

Besides, Renault already sells its Zoe battery electric, which means the equivalent Mk5 Clio needs another drivetrain. In this case, it’s a hybrid, although its crossover cousin, the Captur, gets a plug-in hybrid drivetrain based on the same system at the end of this year.

So far, there have been only two hybrid superminis: Honda’s Jazz hybrid and Toyota’s Yaris hybrid, which, since 2011 and 2012 respectively, have proven that you can (just) make money with a tiny hybrid. Renault aims to do the same with its Clio E-Tech hybrid, which goes on sale this year at about £25,000.

The E-Tech project started about eight years ago, when the French government challenged its home car makers to come up with eco cars for the end of the decade capable of fuel consumption in the range of 150mpg. By the 2014 Paris motor show, we were looking at Renault’s Eolab concept, heavily aero styled with a plug-in hybrid drivetrain that included a three-speed clutchless transmission. The 75bhp 1.0-litre three-cylinder petrol engine, 53bhp electric motor and 6.7kWh lithium ion battery gave an NEDC fuel consumption of 282mpg, with 22g/km CO2 emissions and an electric-only range of 40 miles.