Using air-con blunts mpg by over 6% in hybrid cars

Air-conditioning systems have a bigger impact on fuel economy in hybrids than in petrol and diesel models, according to research by Emissions Analytics.

Testing at the data service’s Los Angeles facility revealed driving a hybrid with the air-con on full reduces mpg by an average of 6.1 per cent, compared to just 3.8 per cent for petrol vehicles and 4.6 per cent for diesels.

• Best hybrid cars to buy now

Economy tumbles even further in hybrids if driving around town, where the effect can rise to nearly 10 per cent. On motorways it fell to 2.8 per cent.

On both types of road, air-con had the least impact on petrol-engined cars’ mpg, with diesels falling in between.

Although the tests were conducted in the hot US climate, where drivers rely heavily on their air-con, Emissions Analytics said the figures still had relevance for UK buyers.

• UK speed limit for lorries increased from 2015

Founder and CEO Nick Molden explained why hybrids suffer more. “This is, in a way, a variant on ‘MPG illusion’,” he said. “The perceived effect on hybrids is worse but the reality is the fuel used is the same as for petrol or diesel vehicles on the same journey.

“When buying a car, it’s important not to be seduced by hybrids’ high headline mpg figures, when under real-world use – including with the air-con on – the mpg can come back down quickly.”