Can underfloor heating mats be used with Carpets?

A foil heating mat is suitable to be used with carpeted floors, the mat is directly laid on the insulation, with the carpet fitted on top of the electric underfloor heating mat.

Is Carpet a good conductor of heat?  

Neither carpet nor underlay are a great conductor of heat, especially when compared to tiles, stone or even wood. So the lower the tog ratings the quicker the warm up time for the electric underfloor heating. Anything with a tog rating of 3 or below will be ideal to be used with the carpet underfloor heating system.