How much extra Fuel does Air Conditioning consume?

[Headtime]

I understand that the A/C in a car puts an extra load on the engine, and as such causes it to burn more fuel.

But is it a significant amount?  How much extra fuel would be consumed by a 1.6l engine in average conditions.

Thanks.

[Impret-Sir]

I have read that running the air-con consumes approximately 1 to 2% extra fuel, on average.

[jake-the-peg]

Hmm looking around the web there seems to be no shortage of opinion on this but I only found one instance of an expreiment to measure it here:

http://64.233.179.104/search?q=cache:ynchLMnGhSgJ:www.transportenergy.org.uk/downloads/TT%2520for%2520Trucksfinal.pdf+%22air+conditioning%22+save+mpg&hl=en

Unfortunately its for a lorry and comes in at 6.5 % increase - a number of the other figures quoted were in that ball park.

[vdub]

Depends on how you drive and how hot the weather is.  Air con uses a lot of power on a hot day - say about 4hp - which could equate to between a 3 and 6% fuel consumption penalty for a 'normal' driver over a mixture of routes.  If you're a more gentle drive, the penalty will be higher in percentage terms -and ironically (becasue your journey takes slightly longer) - the absolute fuel used will be slightly higher too!  Dont forget you can always turn the air-con off, which effectively means you're using no extra fuel - this way you get the best of both worlds over a year

[Headtime]

cheers all, very helpful.