Bill,
The A/C compressor, and power steering pump, are electric, not an ICE belt driven accessories in the TCH. My ICE shuts off when I pull up to a traffic light but the A/C keeps going just fine...
According to my Shop Manual the ECO function is not a customizable option in the A/C system...
My pet peeve with the ECO is the way the switch was mounted out of the way... When I first tried to use it I opened the gas hatch by mistake...

Personally, I haven't noticed any difference gas in mileage when using the ECO mode ...
Wayne
2008 Toyota Camry Hybrid, Magnetic Grey, XM Radio, Body Side Moldings, Splash Guards, Formula 1 Pinnacle 35 Ceramic Window Tint, PadsPlus Neoprene Rubber Insert Set, Putco Chrome Door Handles, Michelin Primacy P215/60R16 95H Tires, SE Rear Spoiler