Fuel saving tips: Drivers warned about the car button that can increase consumption by 20 percent

“Using air conditioning can increase fuel consumption by up to 10 percent, but opening the windows at higher speeds can increase fuel consumption by up to 20 percent.”

A number of other studies have also followed, one of which found that the fuel economy of hybrid cars is more affected by the use of air conditioning than conventional combustion-only cars.

Further research, from Emissions Analytics, found that the impact of air conditioning on hybrid fuel economy was nearly double that.

Fuel efficiency fell 6.1 percent on average for a hybrid car, compared to just 3.8 percent for a standard gasoline car and 4.6 percent for a diesel vehicle.