I bought this meter which I think made in china type

http://www.freemalaysiatoday.com/category/...er-to-illegals/

and connect it in such a way Main Power Source -> Air Cond ON/OFF Switch -> Meter -> Aircond

The Meter will tell you how many watts that your Aircond use per month. (Of course u need to calculate the unit watts multiply with RMx.xx/unit)