The relevant figure is 26.3TWh/55.4TWh = 47% increase each year (or, x1.5 per year). The model of growth should be logistic and not linear (see Marchetti's curves by Luis de Sousa).

In other words, if in 2009 the installation was 10GW, in 2010 one should expect 15GW, in 2011 22.5GW, and so on, and the rate should slow down only when penetration is a substantial fraction of the total...

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