China had built 125 GW of solar power by the end of 2017 and had build 48 GW of solar power in 2017. By the end of 2016, total PV capacity had increased to over 77.4 GW. The contribution to the total electric energy production remains modest as the average capacity factor of solar power plants is relatively low at 17% on average. Of the 6143 TWh total electricity produced in China in 2016, 66 TWh was generated by solar power, which is 1.07% of total electricity production.
China spent $86.5 billion on the 48GW of solar.
With current technology, solar panels capable of generating 200 GW would likely cover 5,000 sq km. Solar power in Saudi Arabia should have a higher capacity factor of about 21%.
With a capacity factor of 21%.
Total Annual Output = 300MW times Capacity Factor 21% times 24 hours in a day times 365 days in a year equals 551,880,000 kWh/year. Moving from 21% capacity factor to 22% means an extra $470k/year.