Solar power plants positioned in space for terrestrial electricity use have been proposed due to the ever-rising world energy consumption and its environmental impacts. This idea is analysed here in the context of sustainability of such power generation. To that end we have performed some new economic, environmental and social effects analysis of electricity generation by solar space power plants of both photovoltaic and solar thermal types power using the best currently available technology. The plants in the analysis were assumed to be in different Earth orbits, or on the Moon built by a robotised factory. One of our results is that both economically and environmentally the best scenario may be to launch a thermal solar power plant to the geostationary orbit from the Moon. Electricity produced in this way could be economically competitive to that generated by fossil fuels on Earth already for as few as 100 space power plants of about 5–10 GW each. This option is also deemed socially responsible with its capacity to reduce poverty with large amounts of cheap clean energy, and environmentally friendly, because it produces more than a hundred times less emissions than the same amount of electricity produced from fossil fuels on Earth.