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Peak-to-average electricity demand ratio climbing across the U.S.

The Energy Information Administration released some potentially troubling news for the power grid February 18.  It appears that the “peak-to-average” ratio of electricity demand is rising in much of the country, particularly in New England.  The peak-to-average demand ratio measures how much higher hourly peak demand is than average hourly demand.  In New England, the EIA found that this ratio has been steadily rising for the past twenty years. As of 2012 peak-hour demand is 78 percent higher than the average level, the highest ratio in the country.  In other words, our highest electric demands are getting larger, while our average demand is remaining the same, or even declining.

New England peak-to-average demand ratio graph showing ratios from 1993 – 2012.  Data courtesy eia.gov.

A high peak-to-average demand ratio means a large fluctuation in daily electricity demand.  Peak demand is getting much higher than average demand in much of the country.  This can affect everything from electricity price to energy availability. As the EIA explains,

This higher ratio translates into decreasing average utilization levels for generators in New England and other regions. Electric systems maintain sufficient capacity to meet expected peak loads plus a reserve margin.

Peak-to-average demand ratios in New York, PJM, and California have also risen over the last twenty years, but not nearly as drastically as in New England.  Other regions such as the Northwest have seen barely any change in peak-to-average demand ratios.

So, what does this mean for consumers?

For one thing, it illustrates some changes in electricity consumption patterns over time.  Higher ratios mean a larger difference in peak versus average energy demand.  Average electric demand seems to be decreasing, while peak demand can spike so high it can stress the grid to its limits.  Differences in climate, housing, economics, population, and several other factors vary drastically in different regions of the United States, so electricity consumption patterns are not the same in every region. But, it is essential that utilities and system operators have some kind of demand-side management plan handy.  This way, system operators and utilities can prevent system failures if that peak demand spikes too much higher than the year’s average.

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