Two things are predicted to be very high on the West Coast this year: the temperature, and gas prices.
That can pose quite a predicament for drivers who want to enjoy the open road but are worried about gas guzzling air conditioning systems draining their fuel tanks and bank accounts. An alternative to the AC is the old practice of simply rolling down the window to keep the cool air flowing, but even that raises concerns about the car becoming less aerodynamic and therefore less fuel efficient.
So what’s the solution to this overheated problem?
There have been several investigations into this issue in recent years. The one thing that everyone agrees upon is that if you can bare it, the most efficient way to travel is to keep your windows rolled up and turn off the air conditioner. That way there is no extra drag on the car and no power drain from the AC.
This, however, is not always possible for obvious reasons. In direct sunlight a car acts like a greenhouse, causing temperatures inside the car to soar much higher than those outside. This can be extremely uncomfortable or even dangerous if the temperature gets too high. So what is one to do?
The website vox.com did a deep dive into the subject in 2014 and concluded that, contrary to some conventional wisdom, it is always more fuel efficient to roll down your windows instead of using the air conditioning, regardless of what speed you are travelling at.
“Good real-world data is frustratingly limited, but the few tests that have been conducted say if you can deal with the sound, it’s slightly more efficient at any speed to roll down the windows, even on the highway,” the article states.
Several sources are cited in coming to this conclusion. One is an article on slate.com which states that the fuel efficiency drop that comes from running your AC varies widely depending on several factors, including your vehicle’s design, but using AC will reduce your fuel efficiency by three to 10 per cent in standard summer temperatures. That number can grow up to 20 per cent during extreme heat, which forces the AC to work even harder.
One long-held belief is that if you get up to a certain speed, the drag produced by open windows causes greater fuel efficiency loss than running the AC does, but that theory has been debunked in a few places, including one test conducted by the Mythbusters team on the Discovery Channel. Other oft-cited tests were conducted by the Society of Automobile Engineers and by Car and Driver.
The fuel efficiency difference was sometimes small for certain tests and conditions, but results always favoured rolling your windows down over cranking the AC up.
The vox.com article concludes: “Bottom line: it’s not a closed case, but all evidence we have shows that rolling the windows down is slightly more gas efficient than using the AC at any speed.”
Now you know the facts. What you do with them, of course, is up to you.
Stay cool out there.
