does central heater waste more electric or small heater?

Answer 1

Waste is a poor phrase to use. The central heater will use more electricity if your interest is to just heat one room, because you will be heating the entire house to get the temperature you want in one room.
If you wanted to heat your whole house and bought a bunch of small heaters, you would end up spending more money then just using your central heating system.
Or, you may want to heat your whole house to some base temperature to keep everything from freezing, and use a small heater to heat a specific room to a comfortable temperature.

Answer 2

Your central heat was designed for the square footage of your home so it will run till needed then shut off however if you go with a small heater chances are it will keep running to keep the area warm and with small space heaters you have to be very careful where to put them as well as making sure small children can not touch them.

Answer 3

More info is needed. It really depends on how energy efficient your furnace is and your room and how big an area you are heating. For instance if you just want to heat one or a couple of rooms a small heater would probably be better because you aren't wasting energy heating rooms you aren't using or aren't in. If you want to heat your whole house the central heat is probably best. I hope this helps.