One example of a heating element includes a first carbon nanotube (CNT) layer and a second CNT layer. At least a portion of the first CNT layer overlaps at least a portion of the second CNT layer, and the first CNT layer includes a first perforated region having a plurality of perforations. Another heating element includes a CNT sheet with a first perforated region having a plurality of perforations and a first perforation density and a second perforated region having a plurality of perforations and a second perforation density different from the first perforation density. A method of forming a heating element includes perforating a first CNT layer so that it includes a perforated region and stacking the first CNT layer with a second CNT layer such that at least a portion of the first CNT layer overlaps at least a portion of the second CNT layer.