On my vehicle (92 Civic) and most others I've seen, the condenser fan comes on whenever the A/C clutch is engaged. This seems like a waste of electricity (and thus fuel) when cruising at 60-75 mph, where the air flow from the fan is going to be dwarfed by air flow from the vehicle's motion. My car has separate radiator and condenser fans (they're mounted side-by-side rather than one in front of the other) so it seems like it would be even more of an issue on vehicles where a single larger fan or pair of fans turn on together.
Any idea if the electrical load is significant to fuel economy? Is there any easy modification that could be made to prevent the fan(s) from running when the vehicle speed is greater than a particular threshold?