Let C₀ be current consumption. Then consumption (C) after t years is:
C(t) = C₀ (1 + 0.1)^t
C(t) = C₀ (1.1)^t
After 10 years, consumption will be:
C(10) = C₀*(1.1)^10
C(10) = 2.5937424601 C₀
Total percentage increase after 10 years:
(2.5937424601 C₀ - C₀) / C₀ = 1.5937424601 C₀ / C₀ = 1.5937424601 = 159.37%
Utility company will have to increase generating capacity by 159.37%