A heating, ventilation, and/or air conditioning (HVAC) unit includes a heater housing having a first side wall, a second side wall opposing the first side wall, and a ceiling extending between the first side wall and second side wall. The HVAC unit also includes a first mounting rail disposed across the first side wall at a first distance from the ceiling, and a second mounting rail disposed across the second side wall at a second distance from the ceiling. The first distance is greater than the second distance. The HVAC unit also includes a heating element assembly coupled to the first and second mounting rails and having a planar heating interface extending from the first mounting rail to the second mounting rail.