A heating apparatus for heating fluid includes a container body, a plurality of electric heater elements, and a support structure. The container body defines a perimeter of a flow path for a fluid flowing through the container body. The plurality heater elements are exposed to the flow path. Each heater element includes a resistance element, sheath, and insulating material disposed about the resistance element between the resistance element and the sheath. The support structure includes a plurality of support sheets. The heater elements extend transversely through each support sheet and contact each support sheet to restrict movement of the heater elements and support the heater elements in the container body. The support sheets contact the sheaths of the electric heater elements to increase heat transfer to the fluid flowing through the flow path. Opposite ends of each support sheet are connected to the container body.