I've got the KX-100 which is the kit version of the X-100-B. It has a 3.2 amp slow blow fuse, so it's ampere requirements are going to be less than that. I'd guess that it would average no more than 2.5 amps when running normally.
If your circuit is already fully loaded then I wouldn't add any more. You might want to get an electrician to come and estimate some electric upgrade options.