The best way to save energy with an air-conditioner is to switch to the "Energy Saver" mode. It consumes less energy, but maintains a standard temperature. While buying an AC, opt for a BEE-rated model and always go for a split AC, instead of a window AC. ACs with BEE ratings consume much less power. An 1.5 tonne AC uses 1.5 units per hour, while an inverter AC uses only 0.91 units per hour.
Old AC (for 5 hours): Rs 27,372
Inverter AC: Rs 16,670