Baseload is the floor of electricity demand. It is the minimum amount of power a grid needs around the clock, day and night, summer and winter. Hospitals, refrigerators, data centers, and streetlights keep drawing power no matter what. That steady hum is baseload.

Utilities plan for it carefully. They sign long-term contracts with power plants that run continuously: nuclear, coal, large hydro, and combined-cycle gas. These plants take hours or days to ramp up and down, so they are suited to steady output. They also produce the cheapest electricity per unit when running at full capacity.

The concept is shifting. As grids add more solar and wind, the demand curve changes shape. Midday peaks flatten. Evening peaks sharpen. Some analysts argue that baseload is becoming less relevant, replaced by flexible generation and storage. Others say a stable foundation is still needed. The debate is really about how to keep the lights on when the wind stops and the sun sets.

Common baseload sources

• Nuclear power
• Coal plants
• Large hydroelectric dams
• Combined-cycle natural gas
• Geothermal plants