Does using air conditioning affect fuel economy?

The debate has started again as to whether using the air conditioning is more fuel-efficient than having the windows down. Which is correct?

Asked on 8 April 2012 by JY, Chewton Mendip

Answered by Honest John
Yesterday, we drove the new Yaris hybrid with windows open and got 4.6 litres/100km (61.4mpg). Today, we drove exactly the same car with windows closed and a/c on and got 3.5 litres/100km (80.7mpg) on the same flat roads in Holland.
Similar questions
We have a 2014 Land Rover Freelander (15,000 miles) and a 2013 Kia Rio (22,000) on 17-inch rims (big mistake for country roads). We have a budget of about £20,000 and would like to change the Kia Rio for...
A couple of months ago my Honda Jazz was doing just over 70 mpg. Then suddenly it went down to 52mpg. I asked at my local garage and they showed me how to have AC turned off. It’s improved a little but...
Like your reader last weekl I acquired (on a lease) a new Hyundai Tuscon Hybrid in January 2025. I have done 6500 miles (varied driving) and have kept a spreadsheet of my MPG and brim the tank each time...
Related models
Fairly big boot by class standards, tempting hybrid option, Toyota has an epic reliability record.
 

Ask Honest John

Value my car

Save £75 on Warranty using code HJ75

with MotorEasy

Get a warranty quote

Save 10% on GAP Insurance

Use HJ10 to save on an ALA policy

See offer