There's a whole menu of different energy sources to choose from in generating electric power—coal, gas, wind and so on—and some are worse for the planet than others. But regardless of where we gather it, the energy itself almost always comes from the sun. Don’t believe me? Let’s think about it: when you burn coal, it reacts with oxygen and releases energy. But where did that energy come from? Prehistoric vegetation.

Ancient ferns and weird swamp trees captured energy from sunlight using photosynthesis. Over eons, all that greenstuff got buried, where heat and pressure turned it into coal. That’s right, coal-based power is solar power. You could even call it a renewable resource, if you don’t mind waiting 100 million years.

Same with oil and natural gas. These fuels come from ancient marine microorganisms like phytoplankton and algae, which again used photosynthesis. Gazillions of these organisms died and settled to the bottom of the sea over time, getting buried in sediment and turning into the sludge we call petroleum. If you see an oil well on land, that spot was probably once underwater.

OK, but hydroelectric? That’s based on the gravitational potential energy of water at high elevations. As it runs downhill in rivers, it can do work, like spinning turbines. Well, how did the water get up there? It was deposited by snow and rain, which came from evaporation of seawater, which is driven by the sun's heat. Yep, solar power.

Wind energy? Well, the sun heats the Earth’s surface, but it does so unevenly. Its rays hit low latitudes more directly than high latitudes, and continents heat up faster than oceans. Result: warm air rises, creating low-pressure areas that cooler air rushes in to fill. We call that wind. So, light energy is converted to thermal energy, and then to kinetic energy in air molecules. Solar.