Abstract: A panel heater for animals of generally rectangular slab-like shape. The panel heater has sloping sides to accommodate animals and comprises basically a shell into which a fire retardant material is poured around electrical resistance wire. Anchorage is provided to ensure that there is adequate keying between the fire retardant material and the shell to prevent degradation during use. Various support devices are provided for the heating element which is formed from an electrical resistance wire. A two-stage pouring of the fire retardant material is used to prevent the possibility of accidents by keeping the electrical resistance wire away from the outer surface.