We constantly hear how wind and solar are now cheaper than fossil fuel generation. I don’t dispute the calculation, however it is misleading.

These cost comparisons are based on the cost of generating an electron. They are not based on generating an electron when you need it. This is a huge difference. If you need an electron when the sun isn’t shining, then what is the cost? The shift in perspective is important. It is not about generation it is about meeting demand whenever the demand is there.

Solar and wind generation are not only intermittent but can be extremely volatile. The output from these resources can decline by 80% in a matter of minutes. Since we still must meet demand, we need to backup these renewables with other sources of energy. Those costs should be taken into account when we compare generation costs.

“The intermittency of wind and solar means that, if always-on electricity is to be supplied, reliable coal, natural gas, and nuclear generators must be maintained as wind and solar systems are added to the power grid. Power system operators know that up to 90 percent of the capacity of traditional generators must remain operational to prevent system blackouts. Therefore, addition of renewables boosts both the capacity and the number of needed systems, raising the cost of electricity.”

“Wind (and solar) systems require more and longer transmission power lines than traditional power plants. Coal, gas, and nuclear plants are located near population centers and tend to be large-capacity plants. These plants can be connected to the grid with relatively short, high-capacity transmission lines. Wind systems tend to be located in remote areas, such as on ridgelines, often far from cities. Wind and solar are spread out over wide areas and require 100 times the land of traditional plants. Longer transmission systems over wide areas need to be deployed for wind and solar, raising system costs and electricity prices.”

This is not to say that we shouldn’t move forward with decarbonizing the grid with renewables. What it does mean is that we need to be realistic.