- 51% of all generating capacity is 30+ years old.
- 73% of all coal plants are 30+ years old
- 24 out of 25 oldest plants (60+ years) are hydropower
- Nearly all nuclear plants are 20+ years old
Here is a graphic from EIA with more detail. The pie chart shows how much generating capacity comes from each fuel type. The graph shows capacity by year the plant was built.
Notice that hydropower was the first energy source built, the creation of coal plants dominated from 1950 to the mid-80s, and it’s been all natural gas since then.
In a nutshell, it is not correct to assign human attributes (e.g., lifetimes) to inanimate objects. Consequently, the operating span of a coal fired power plant can be unlimited since any degraded or failed component can be replaced with a new one. The decision on whether to make a refurbishment, or to build a new plant, is merely a question of relative economics and investment risk. For example, the cost of a single replacement part is almost always less than the cost of replacing the plant. However, in an old plant, there is a risk that many additionally worn parts also will need replacement soon. Plant owners evaluate these tradeoffs each time a major component fails and make the decision whether or not to retire the plant.