The Baltic Cable is a monopolar HVDC power line running beneath the Baltic Sea that interconnects the electric power grids of Germany and Sweden. Its maximum transmission power is 600 megawatts (MW). The Baltic Cable uses a transmission voltage of 450 kV – the highest operating voltage for energy transmission in Germany. The total project cost was 2 billion SEK (US$280 million), and the link was put into operation in December 1994. With a length of 250 kilometres (160 mi), it was the second longest high voltage undersea cable on earth, until Basslink came into service in 2006.