Abstract: An apparatus for heating petroleum, petrochemical, chemical process fluids, and boiler feed water or steam generation with a combination, or individual operation, of electrical elements and fired burners. The apparatus includes a radiant heating section and a flue gas stack for exhausting a combustion gas to the atmosphere. The radiant section includes one or more process coils, one or more fuel-fired burners for combusting a fuel and producing the combustion gas, where the one or more fuel-fired burners are arranged to provide radiant energy to a first area of the one or more process coils, and one or more electrical heating elements arranged to provide radiant energy to a second area of the one or more process coils. The one or more electrical heating elements are configured to provide 5% or more of a combined maximum energy output of the fuel-fired burners and the electrical heating elements.