 How has shale gas impacted the power grid? Electric power is really the fastest growing source of demand for natural gas. And over the past several years, natural gas has been really rapidly supplanting coal for power generation. So the amount of coal we use for power generation has gone way down, and the amount of natural gas we use for power generation has gone way up. Natural gas is also just starting to supplant nuclear power. And so what's going on here is basic economics. Natural gas has gotten so cheap that there are lower costs to generate electricity with natural gas than for coal, and increasingly lower costs to generate electricity with natural gas than nuclear. How natural gas competes with renewables is a different story and one that's changing really rapidly. So we tend to make these cost comparisons using a number called the levelized cost, which is basically like an average cost to produce electricity from some fuel source. And so if you look at the levelized cost for gas versus the levelized cost for wind or solar, you'll see that right now renewables are several times more expensive than natural gas to produce electricity. But the costs for wind and solar are coming down so fast that within five or ten years it may well be the case that renewables are cost competitive with natural gas for generating electricity.