Energy efficiency through distributed load shedding

Managing power consumption peaks is a major challenge facing electrical power suppliers and operators. Our network’s viability depends on the balance between electricity supply (production) and demand (consumption). However, increasing peak demand threatens to disrupt that balance and cause massive and frequent blackouts. Distributed load shedding seems to be a pragmatic response to this problem.


Although increasing electricity demand is met by production, the frequency of peak periods has become a source of concern. While our consumption grows by an average 0.6% every year, peak periods increase at a rate of 3% a year, with a dramatic 14% increase between 2005 and 2012. Both the growing overall demand and the increasingly frequent peak periods can be explained by a series of factors, such as the many cold waves as well as the growing number of domestic appliances and the use of electric heaters (31% of French households, i.e. the highest percentage in Europe). Poor consumption forecasts can lead to peak periods, insufficient production and possible blackouts. There are two solutions to manage such unbalances. The first consists in temporarily increasing power generation by turning on peak power plants (coal, oil and gas), which is not an appropriate long-term solution because of high CO2 emissions. The second, more promising method known as load shedding or curtailment seeks to reduce demand to make it match supply. Curtailment consists in shutting down a number of sources of electrical power consumption at the same time and can affect households and industry alike. Under a decree issued by the Ministry of Ecology, at peak times electricity-intensive industries (aluminium, chemistry) may be asked to voluntarily stop their consumption from 15 minutes to 1 hour in exchange for a discount on their next bill.

Distributed load shedding consists in reducing global electricity consumption by imposing cut-offs on many households at the same time. Curtailment can affect heating or A/C and must last long enough so as to rebalance supply and demand, but not to the extent that it would cause discomfort to consumers. In order to impose temporary cut-offs, a load shedding operator remotely controls household electricity consumption units via a device installed on the electricity metre.

“The cheapest form of energy is that which is not consumed”

Obviously, the main issue at stake is the environment. Using distributed load shedding on a large scale could avoid consumption peaks and the use of CO2-intensive peak power plants, as well as sharply reduce electricity production. If the 7 million households relying on electric heating chose distributed load shedding, 10 to 20 gigawatts could be saved every day during a cold wave. Besides, it would contribute to better integrating renewable energy sources to the network. Whereas developing renewable electricity is a difficult task, because it is intermittent and difficult to store, load shedding overcomes insufficient supply by reducing demand.

According to the EU directive on energy efficiency (directive 2012/27/EU of the Parliament and the Council on energy efficiency passed on October 25, 2012), “the cheapest form of energy is that which is not consumed”, a principle underlying the load shedding method. Imposing cut-offs means shutting down consumption units and therefore cutting demand and electricity bills. However, load shedding might have a delayed impact on consumption, i.e. savings achieved might be partly offset by higher consumption when power is back (for instance to restore the desired temperature).

The ratio of electricity saved on a day with imposed load shedding to the daily consumption of an average household ranges from 6.8% and 8.3% (test conducted by ADEME and CSTB from January to March 2012 on a sample of 2,800 people). However, according to the ADEME (French agency for the environment and energy management), that does not mean that the same percentages will be saved on the next electricity bill, because of the differences in current pricing systems. The remote control devices used to impose load shedding can also provide users with a lot of information which could work as an incentive for them to consume less; however it will be necessary to ensure that grid operators guarantee the confidentiality of the data submitted and respect consumer privacy.

This fledgling method opens the way for a new market and new solutions nationwide to preserve our energy security while enabling us to fulfil our environmental commitments.

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