The power grid in the continental U.S. is a tiered system that encompasses three major interconnections. The Eastern and Western grids tend to operate independently, although they permit power to be transferred between grids. Not to be confused with utility companies, who are the balancing authorities (grid operators) who work within the Eastern and Western Interconnections. Grid operators ensure the balance between supply and demand in real-time. This allows for safe, reliable power system operation. Without the supply and demand balance, there is a risk of local and regional blackouts. Everything east of the Rocky Mountains and part of northern Texas is in the Eastern Interconnection. The Eastern Interconnection has 36 balancing authorities, which includes five in Canada. The Western Interconnection extends west of the Rockies and has 37 grid operators, including two in Canada and one in Mexico. The Electric Reliability Council of Texas (ERCOT), the name of the grid operator and the regulatory body's name, is solely responsible for most of Texas.