Why nuclear leads fossil fuels in output consistency
A nuclear plant operates continuously at full power unless shut down for refueling (typically every 18-24 months for a few weeks) or maintenance. This translates to capacity factors of 90-93 percent in most developed grids. Coal plants achieve 45-60 percent, limited by maintenance downtime and demand fluctuations. Combined-cycle gas plants reach 45-55 percent, with the efficiency advantage over coal offset by their role as peak-load followers in renewable-heavy grids.
The difference is structural: nuclear plants are designed for baseload operation; their high capital cost ($10-20 billion) demands maximum utilization. Coal requires regular unplanned downtime for emission-control maintenance. Gas plants are built for flexibility and rarely run at rated capacity for months straight.
Intermittency and the capacity factor ceiling for renewables
Wind turbines are rated for their peak output in strong wind, but average wind speeds deliver 30-40 percent of that rating, yielding capacity factors around 35-40 percent onshore, up to 50 percent offshore. Solar panels see sunlight at full intensity only a few hours per day, even in cloudless conditions, averaging 20-25 percent capacity factor across most regions (slightly higher in deserts). These are not design failures; they reflect the physics of diffuse energy sources.
Capacity factor is therefore the single most useful metric for comparing energy sources on an apples-to-apples basis. A 100 MW nuclear plant delivers 90 times more energy over a year than a 100 MW solar farm in an average location. This is why renewable grids require massive overbuilding and storage: a 500 MW wind farm plus 500 MW battery storage still delivers only what a 200 MW nuclear plant provides on-demand.