I remember hiring a car someway back - a little car but one with AC. It was a hot day, I was climbing a hill and switched the AC on. The result was as if the mother-in-law had just leapt into the back seat, weighing it down.
a lot of it is dependant on engine size, when a/c is turned on with a small engine you can actually feel the drop in power with a larger engine hardly noticable,the engine needs to drive the aircon pump hence the extra effort .
Answer to your question is yes, but it really varies vehicle to vehicle and is quite minimal.
We are told by motoring "experts" that a 5-10% incrase MAY be experienced.
What should be borne in mind is that NOT using the A/C for long periods can lead to having problems with system which are VERY costly to rectify. It appears that you pays you money and takes your choice,