Modern air-conditioning is more energy-efficient than ever, but people are still conscious of unnecessary waste when systems are left running in unoccupied rooms. To combat this, there are several movement-sensor products, of various degrees of sophistication, which turn systems off when no movement is detected after a pre-set period. Yet these have drawbacks, as some are connected direct to the mains supply and simply interrupt this, but most systems do not like being switched off in this way and require several seconds to re-balance their gas/liquid levels. Normal de-activation allows this shut-down process whereas cutting-off at the mains does not.
Some quality systems incorporate their own movement sensors which, rather than de-activating entirely, slow down to low-running when no movement is detected. At the budget end are battery-operated sensors which 'learn' the system's 'Off' signal and emit this after a pre-set period of no movement. For rental properties, a simple measure can be to provide clients with remote controls that are 'locked' to run at moderate temperatures only.
Different scenarios require different solutions - for sensible advice, call Penguin NOW!