An insert intended for electrical furnaces and of the type that includes an insulating shell having an outside and an inside having a rotationally symmetrical, e.g., cylindrical shape, and a heater element that is arranged inside the insulating shell and extends several turns in a continuous loop having an overall shape corresponding to the rotationally symmetrical shape of the insulating shell. The continuous loop includes spaced-apart bends, which divide the same into individual sections of limited length to which occurring thermal expansion is isolated locally. In an exemplary embodiment, the bends are U-shaped to impart to the continuous loop a meander shape. Another exemplary embodiment relates to a heater element.