A subsea direct electrical heating assembly adapted to heat a hydrocarbon conducting steel pipeline (1) arranged subsea. The assembly comprises a direct electrical heating cable (3) extending along and being connected to the steel pipeline (1) and a power transmission cable (7) receiving electric power from a power supply (5) which is arranged onshore or at surface offshore, and which feeds the direct electrical heating cable (3). The subsea direct electrical heating assembly comprises a power conditioning arrangement (100) arranged at a subsea location, in a position between the power transmission cable (7) and the direct electrical heating cable (3). The power transmission cable (7) extends from the offshore or onshore power supply (5) and down to the power conditioning arrangement (100).