get a watt meter, like "kill a watt". plug your equipment in and it will measure your consumption, normally the watt fluctuate up and down, just get an average, like 100 watt, then assume that equipment will take 100wh(watt hour) if run for 1 hour, if you are paying RM0.50 per kwh(kilowatt hour) then that piece of equipment will cost you RM0.05 per hour.

its good to measure, cause that is the most accurate, like a monitor say its power draw is 15 watt, u dont know how they measure it, its very different if you set your brightness up and displaying a bright image, compare to almost black. same to air con, freezer, etc, those equipment will take alot of power when their motor is running and will take little when they are cold enough, and they will draw more and more when they are old and inefficient. apply same to your table fan, if you turn your table fan max, it will draw more power compare to minimum speed, also same apply to your PSU inside your CPU, even it label 500watt, most likely u are only using 100watt until u start playing game which your GPU draw alot of power which perhaps drawing up to 300watt, very low change u are drawing 500 watt flat, cause if that happen, most likely your PSU exploded long ago.