With power demand running 2,000 Mw above forecasts, the California Independent System Operator issued a Stage 2 emergency Monday signifying the reserve margin has fallen to less than 5%.

The grid operator said power demand is up due to temperatures that are 5-6° F. hotter than meteorologists predicted. Because the heat wave is regional in nature, levels of imported power have decreased as other states, especially those in the Southwest, also cope with high demand for power, the ISO said.

In addition, 1,500 Mw of imported power was also reduced when a two-unit power plant that serves southern California tripped off line over the weekend. Despite predictions of summer outages, the ISO in June managed to avoid rotating blackouts.

Peak demand on the transmission system is expected to reach about 40,000 Mw about 4 p.m. PST. The ISO called for conservation during the peak afternoon hours.

The Stage 1 and 2 declarations, expected to be in effect until 6 p.m., allow the California ISO to access emergency resources to help maintain operating reserves.

The ISO put the state utilities on notice large commercial customers that have signed up to voluntarily curtail power during high demand days could be asked to do so. If an operating reserve shortfall of less than 1 1/2% is unavoidable, Stage 3 is initiated. Involuntary curtailments of service to customers including “rotating blackouts” are possible.