Abstract: A fluid heating device which comprises a non-conductive magnetic core having a primary winding of an electrically conductive wire. A secondary electrically conductive jacket surrounds or is concentric with the primary winding in close contact therewith through a thermally conductive and electrically non-conductive medium. The primary winding has an input connection connectible to a voltage supply source. A power control device is connected to the input connection. The secondary electrically conductive jacket has passages therein for the flow of a fluid, at predetermined flow rate, from an input to an output of the passages. The fluid extracts heat from the secondary conductive jacket, generated by joule effect, whereby to heat the fluid and simultaneously cool the jacket to maintain the secondary electrically conductive jacket at a substantially constant temperature.