Just about the same as any other eletrical heater - they are all very efficient and have the same running costs apart from night storage heaters on a special tarrif which will be more economical in power consumed costs.
Calortec heaters tend to cost more (much more) and generally do not have a good reputation - the advertising and the claims made are alleged to be quite misleading.
Their agent on earth, Peter Lambert replies several times on here - not since Oct 2009 - and speaks glowingly without being specific.
Search on here using the word Calortec in the box on the top right and form your own opinion.
Search also on Google using the words Moneysaving Calortec
Good luck...
Peccavi
February 2010