A compact and highly efficient intravenous fluid heater includes a heat exchanger assembly, sensors for sensing respective temperatures of entering and exiting fluids of the flow path, a controller for controlling the heat generated by the heat exchanger assembly, based upon the temperatures of the exiting fluids, heating of the fluid in the flow path by the heating element so as to cause the fluid in the flow path to be substantially uniformly heated to a desired infusion temperature prior to exiting the heater. The heat exchanger assembly uses thin film heating elements having a predetermined set temperature and that transfers heat directly to a standard intravenous tube coil wrapped around the battery housing. The intravenous fluid heater is located in a housing with the intravenous fluid lines extending there from for standard connection with an intravenous line or source of intravenous fluid.
