Total power generated doubles every 3 years, so the growth rate is: (final value / initial value)^(1/years) - 1 = (2 / 1)^(1/3) - 1 = 26% For the formula, the initial capacity was 92 thousand megawatts, so as a function: WW = Initial Capacity*(1 + growth rate)^(tt) WW = 92*(1+26%)^(tt)