The wind doesn't blow and the sun doesn't shine all the time - so renewable critics often question how wise it is to build power grids around resources that often don't run
At a more granular level, dispatchable and non-dispatchable power sources need to be combined to solve for generation demand and ultimately peak demand and capacity margins
Capacity factors can be calculated by looking at monthly generation versus capacity. We've shown some of this work at the state level before but U.S. factors are shown to highlight generally low capacity factors for all fuel sources outside nuclear power
Coal and nuclear are generally considered baseload fuel sources. Reliable, high capacity factor generation for lower, non-peaking demand.
Nuclear power seems to be at the early stages of a renaissance in the U.S. and globally. We are fans of incentivizing nuclear power and one need look no further than long-term capacity factors to know why.
Coal on the other hand has seen a downtrend for decades, recently dipping below 40% before much higher natural gas prices brought some coal power back into-the-money.
It is worth noting coal capacity factors rolled over long before wind and solar capacity ramped in the U.S. Low natural gas prices were undoubtedly the primary driver of killing off coal power across the country.
Natural gas is a straddle fuel. Gas plants can be used for baseload or peaking power. Gas capacity factors have been quite low in the U.S. Recently at 34%, gas plant usage was below 20% in the early 2000's when a wave of deregulation led to a massive gas power plant build-out and glut of capacity.
Combined cycle gas turbines (CCGT) run a much higher capacity factors than simple cycle combustion turbines (SCCT). We'll show that in some future work.
Trailing 12-month wind capacity factors are about 3% higher than natural gas.
Utility-scale solar is locked in around 25% for the last 7-8 years. Note that we dove into behind-the-meter capacity factors in Distributed Solar in the U.S.
Finally, hydroelectric roughly splits the difference between wind and solar.
Power markets are regional so it is hard to generalize from this data but it would suggest the challenge faced by U.S. power markets to ensure reliability is to co-mingle a number of energy sources that all operate at low capacity factors.