A heating device for use thereof in a vehicle and configured for heating a fluid, which device comprises: - a chassis (1.1) comprising a chamber for the thermal fluid; - an inlet port for the entry of the thermal fluid; - an outlet port for the exit of the thermal fluid wherein the inlet port is in fluid communication with the outlet port through the chamber; - at least one heating plate (1.2) fixed to the chassis (1.1) comprising on a first side a heat generation region, and a second side, opposite the first side, forming part of the internal wall of the chamber; wherein the heat generation region comprises at least one electric resistor (1.2.2), P characterized in that the heating plate (1.2) has an essentially rectangular configuration with the inlet port and the outlet port in correspondence with one of the smaller sides of the rectangle, wherein the heating device further comprises three dissipating elements (1.3), with these three dissipating elements (1.3) being on the second side and positioned in correspondence and in thermal communication with at least one part of the heat generation region, wherein the three dissipating elements (1.3) are made of aluminum, wherein each of the three dissipating elements (1.3) comprises fins (1.3.1) distributed according to a longitudinal direction, wherein the three dissipating elements (1.3) are a first, a second and a third dissipating element, wherein the three dissipating elements (1.3) determine a family of routes according to a broken straight path from the inlet port to the outlet port, wherein the broken straight path is configured in a "U" shape, such that: the first and the third dissipating element extend along a direction established by a larger side of the rectangle, and the ends of the first and third dissipating elements located on the opposite side where the inlet port and the outlet port are located have a chamfered termination, leaving a free area occupied by the second dissipating element having an essentially triangular configuration. - a chassis (1.1) comprising a chamber for the thermal fluid; - an inlet port for the entry of the thermal fluid; - an outlet port for the exit of the thermal fluid wherein the inlet port is in fluid communication with the outlet port through the chamber; - at least one heating plate (1.2) fixed to the chassis (1.1) comprising on a first side a heat generation region, and a second side, opposite the first side, forming part of the internal wall of the chamber; wherein the heat generation region comprises at least one electric resistor (1.2.2), P characterized in that the heating plate (1.2) has an essentially rectangular configuration with the inlet port and the outlet port in correspondence with one of the smaller sides of the rectangle, wherein the heating device further comprises three dissipating elements (1.3), with these three dissipating elements (1.3) being on the second side and positioned in correspondence and in thermal communication with at least one part of the heat generation region, wherein the three dissipating elements (1.3) are made of aluminum, wherein each of the three dissipating elements (1.3) comprises fins (1.3.1) distributed according to a longitudinal direction, wherein the three dissipating elements (1.3) are a first, a second and a third dissipating element, wherein the three dissipating elements (1.3) determine a family of routes according to a broken straight path from the inlet port to the outlet port, wherein the broken straight path is configured in a "U" shape, such that: the first and the third dissipating element extend along a direction established by a larger side of the rectangle, and the ends of the first and third dissipating elements located on the opposite side where the inlet port and the outlet port are located have a chamfered termination, leaving a free area occupied by the second dissipating element having an essentially triangular configuration. the first and the third dissipating element extend along a direction established by a larger side of the rectangle, and the ends of the first and third dissipating elements located on the opposite side where the inlet port and the outlet port are located have a chamfered termination, leaving a free area occupied by the second dissipating element having an essentially triangular configuration.