French shops will have to close their doors when using air conditioning under a ruling designed to cut energy use.
The rules are soon to be rolled out across France, with some areas already having adopted the policy drawn up by minister Agnès Pannier-Runacher.
Shops will be fined up to €750 (£640) for breaking the rule, as France looks to tighten its energy usage due to pressures resulting from increased costs after Russia invaded Ukraine.
Ms Pannier-Runacher told RMC radio that it is “absurd” that shops would leave the air-con on and open their doors.
She told the Journal du Dimanche newspaper: “(We will) ban shops from having their doors open while the air conditioning and heating are working."
She added that “there will (also) be a ban on illuminated advertising, whatever the size of the city,” between 1am and 6am - which is already in place for smaller places. Airports and stations will be exempt.
The news comes as Shell released a warning that rationing of power supplies cannot be ruled out.
Much of Europe is continuing to feel extreme heat this week following widespread wildfires.
French residents were last week warned of a “heat apocolypse” while more than 16,000 were evacuated.