The Electric Grid, Energy Demands and Nuclear Power Plants

Neil Sheehan
Public Affairs Officer, Region I

A question we receive with some frequency from reporters involves how the grid copes with the power loss when a large baseload electricity producer such as a nuclear power plant suddenly goes off-line. Put another way, what keeps the lights on, the coffee-maker brewing and the refrigerator humming along when a reactor in their area isn’t in operation?

gridThis question takes on greater urgency during peak energy demand seasons, summer being number one in this regard thanks to all of the air-conditioners merrily cranking away as temperatures creep up.

The simple answer is that the various grid operators, like the Boy Scouts, always strive to be prepared. They do this by maintaining power reserves, though the amounts available can vary by region. So-called “peaker” power plants can be called into service when necessary to help maintain sufficient electricity flows.

Of course, since nuclear power provides about 20 percent of the electricity used in the U.S., close tabs are kept on the status of the nation’s reactors, especially during times of peak demand. The NRC makes that information available to the public on its website each day.

Here is a handy graphic compiled by the U.S. Energy Information Administration (EIA) that provides a good summary of reserve margins for the various grid operators around the country.

As the EIA so succinctly states, “The electricity industry uses a simple strategy for maintaining reliability: always have more generating and transmission capacity available than may be required, taking into account unexpectedly high demand or the possibility of unplanned outages of generators or a major transmission line.”

The good news is the reserves are projected to be sufficient as the summer of 2013 rolls on.

In addition to the EIA, another good source of information on U.S. power reserves is the North American Electric Reliability Corp.