According to “cautiously optimistic” power executives, the US power grid should be reliable over the coming months, but energy secretary Bill Richardson has warned that power demand could exceed projections. The news comes in the light of forecasts for hotter than normal weather this year.

Richardson’s remarks followed the North American Electric Reliability Council (NERC) summer assessment, detailing predictions for the next few months. While most regions seem reasonably confident, certain, often urban, areas may face restrictions where transmission capacity is limited. For instance, key transmission outages in the Northeast may restrict imports into the area at peak demand, said NERC.

According to Michael Gent, president of NERC, generation and transmission resources are expected to meet projected demands in most areas this summer, although higher than estimated demand due to hot weather, or unexpected outages, may strain electric supplies. Peak demand for electricity is expected to be around 675 GWe, roughly 1.7 per cent higher than last year, although NERC added that an additional 10 GWe would be available in the Southeast, 5 GWe in Texas and other new capacity in the Midwest and Alberta in Canada.

Along with New York and New Jersey, utilities in California, Arizona, New Mexico and Nevada could face shortages. NERC pointed out that last summer was cooler than usual and, if temperatures return to normal, Southwestern states could be vulnerable. And, although capacity appears adequate, it is often reliant upon unconfirmed energy purchases, said NERC.

However, the reassurances from NERC must have done little for consumers in California, when searing temperatures unexpectedly early in the year left the power system straining to meet demand. With some 6 GWe of capacity off-line for maintenance or repair the state scrambled to buy in power.

Although Southern California Edison called in around 500 MWe of interruptible capacity, the unseasonably hot weather at the end of May resulted in the Californian Independent System Operator issuing a stage two alert, where reserve capacity reaches five per cent of demand and interruptible contracts are exercised, when this margin falls to just 1.5 per cent, rolling blackouts are expected.

Senior figures within the industry have issued statements that all should be well during the summer months, when temperatures and demand are most likely to peak. But, with a southwest heatwave predicted as Modern Power Systems goes to press, California’s energy system is still facing a tough test of reliability.