U.S. grid regulators warned that North America’s electric power system is not expanding fast enough to meet rising demand, meaning that several regions are at heightened risk of shortages over the next five years.

The North American Electric Reliability Corporation released its long-term reliability assessment, warning that generation and transmission growth are lagging for what is needed to support large loads, such as data centers. It also noted that shifting electricity supplies away from weather-dependent sources, such as solar panels and wind turbines, and reducing fuel diversity increases the risk to grid reliability.