depends on the base temp, if your room already at 29degrees temp and you set your AC to 22degrees, of course the AC will do minimal work compared to a 35 degrees, hence much efficient.
If you mean to leave it on 24/7, its not technically power efficient since the AC still continues to maintain the temperature, once it reaches the temperature you set, it will rest for abit, and whenever it gets hotter again, it will use much more energy again to maintain it.
Conclusion: The most power efficient way is to just turn it off 24/7 ayon wala talaga konsumo.