Comment by science4sail

* That Wikipedia link gives an average global energy consumption of 4.810^12 watts (assuming 11.63 TWh per MToE). The solar insolation of Earth is about 210^17 watts The total power output of the Sun is about 410^26 watts. The total solar power output of the Milky Way galaxy is about 410^37 watts

Assuming exponential growth and assuming 20% utilization, that gives us

A fully solar economy in ~13 years * Kardashev Type 1 in ~59 years * Kardashev Type 2 in ~272 years * Kardashev Type 3 in ~381 years