The easy way to calculate which power you need is that a Calortec radiator will heat in average a square meter with 100 W. This based on a room with an average highte of 2,50 m and an normal insullation. So for example for a 10 square meter room you need a 1000 W (1KW) radiator (10 square meter times a 100 W = 1.000 W radiator).
If you have a larger room there are radiators until 2.000 W! It is ofcourse always more comfortable to install 2 radiators in the room. In that way you will have a more even spread warm and comfortable feeling.
Currently you will find a very nice VT about the ceramic Calortec radiators on the Ideal World site, there you will find a lot of info.
Peter Lambert, October 2009