Many of us might assume that the reason so much energy still comes from gas and coal power plants is simple economics: those fuels are cheaper. But though it was once true, that assumption has actually been obliterated by a recent decline in solar and wind costs over the past decade. When it comes to the cost of energy from new power plants, onshore wind and solar are now the cheapest sources—costing less than gas, geothermal, coal, or nuclear.

Solar, in particular, has cheapened at a blistering pace. Just 10 years ago, it was the most expensive option for building a new energy development. Since then, that cost has dropped by 90 percent, according to data from the Levelized Cost of Energy Report and as highlighted recently by Our World in Data. Utility-scale solar arrays are now the least costly option to build and operate.