New Delhi, May 22 -- Ask families in Germany and the UK what happens when more and more supposedly cheap solar and wind power is added to the national mix, and they will tell you by looking at their utility bills: power gets far more expensive. This defies everything we're being told. Green energy is supposed to be incredibly cheap. But we're not hearing the real story.

The idea that power should get cheaper as we get more green energy is only true if we exclusively use electricity when the sun is shining and the wind is blowing. But modern societies need power round-the-clock. When there is no sun and wind, green energy needs plenty of back-up, often powered by fossil fuels. This means that we pay for not one, but two power systems. And...