To give an idea of the scale of the problem, assuming a solar panel mass of 20 kg per kilowatt (without considering the mass of the supporting structure, antenna, or any significant mass reduction of any focusing mirrors) a 4 GW power station would weigh about 80,000 metric tons, all of which would, in current circumstances, be launched from the Earth. This is, however, far from the state of the art for flown spacecraft, which as of 2015 was 150 W/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.