Disclosed herein are more energy efficient heaters for dispensing volatile air treatment chemicals. The heaters have a housing with a base and a cover, the base and cover together defining an enclosure with an internal generally ring-shaped cavity and an axial through bore. One of the base and cover has an essentially cylindrical extension that is integral therewith, extends towards the other of the base and cover, and forms a portion of the axial through bore. First and second electrical contacts are positioned in the cavity with portions overlapping against a heater. A metallic heat transfer sleeve formed separately from the base and cover is positioned radially outward and around the essentially cylindrical extension, and has a flange abutting one of the contacts. Also disclosed are dispensers that incorporate these heaters.