 This is, however, far from the state of the art for flown spacecraft, which as of 2015 was 150W/kg (6.7 kg/kW), and improving rapidly.Very lightweight designs could likely achieve 1 kg/kW, meaning 4,000 metric tons for the solar panels for the same 4 GW capacity station.Beyond the mass of the panels, overhead (including boosting to the desired orbit and stationkeeping) must be added.