AC vs. MPG: impact of air conditioning on fuel economy tested

[MetroMPG]

How much extra fuel does the Micra burn running the A/C ? ENQUIRING MINDS WANT TO KNOW!

Just for kicks, I did a series of bi-directional averaged runs at 3 different speeds with the A/C on and off.

I set the fan on the 2nd speed and left it there for all runs, just toggling the A/C switch.

Here's what I saw:



The average fuel consumption increase with A/C on vs. A/C off was 0.3 L/100 km or 5.9%.

Here are the raw numbers...

speed   AC      N.      S.      avg L/100 km*

60      off     4      4.1      4.05
        on      4.3    4.4      4.35
        on      4.3    4.5      4.37
        off     4.2    4.1      4.16
                        
80      off     5      4.5      4.75
        on      5.5    4.7      5.10
        off     5      4.5      4.75
                        
100     off     6.3    5.6      5.91
        on      6.6    5.8      6.15

(* Some of the averages are affected by rounded conversions of initial 
readings that were taken in MPG)