[citation needed] They generally shut down or reduce power only to perform maintenance or repair or due to grid constraints.
[citation needed] The duration of operation for peaking plants varies from a good portion of the waking day to only a couple of dozen hours per year.
The status of the electrical grid in that region, especially how much base load generating capacity it has, and the variation in demand are also very important.
[citation needed] Where hydroelectric dams or associated reservoirs exist, these can often be backed up, reserving the hydro draw for a peak time.
A plant with a reservoir that holds less than the annual river flow may change its operating style depending on the season of the year.
Their startup or shutdown took many hours as they were designed to operate at maximum power, and heating up steam generators to the desired temperature took time.
[7] Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope, up to 140 MW/minute.
[7] Nuclear power plants in France operate in load-following mode and so participate in the primary and secondary frequency control.
[10][11] In countries where the baseload was predominantly nuclear (e.g. France) the load-following mode became economical due to overall electricity demand fluctuating throughout the day.
[12] In markets such as Chicago, Illinois where half of the local utility's fleet is BWRs, it is common to load-follow (although potentially less economic to do so).
[12] Modern CANDU designs have extensive steam bypass capabilities that allow for a different method of load following that does not necessarily involve changes in reactor power output.
Bruce Nuclear Generating Station is a CANDU pressurized heavy water reactor that regularly utilizes its ability to partially bypass steam to the condenser for extended periods of time while the turbine is operating to provide 300 MW per unit (2400 MW total for the eight-unit plant) of flexible (load following) operation capabilities.
In fact they clean the ambient air by extracting PM2.5 particulates and also generate pure water for drinking and industrial applications.
For countries that are trending away from coal fired baseload plants and towards intermittent energy sources such as wind and solar, that have not yet fully implemented smart grid measures such as demand side management to rapidly respond to changes in this supply, there may be a need for dedicated peaking or load-following power plants and the use of a grid intertie, at least until the peak blunting and load shifting mechanisms are implemented widely enough to match supply.
[27] The decentralized and intermittent nature of solar and wind generation entails building signalling networks across vast areas.
In 2010, US FERC Chairman Jon Wellinghof outlined the Obama administration's view that strongly preferred smart grid signalling over dedicated load-following power plants, describing following as inherently inefficient.
Due to the very high cost of dedicated battery storage, use of electric vehicle batteries both while charging in vehicles (see smart grid), and in stationary grid energy storage arrays as an end-of-life re-use once they no longer hold enough charge for road use, has become the preferred method of load following over dedicated power plants.
Such stationary arrays act as a true load-following power plant, and their deployment can "improve the affordability of purchasing such vehicles...Batteries that reach the end of their useful lifespan within the automotive industry can still be considered for other applications as between 70-80% of their original capacity still remains.
The number of such batteries doing nothing is increasing rapidly, e.g. in Australia where Tesla Powerwall demand rose 30 times after major power outages.
[29] Home and vehicle batteries are always and necessarily charged responsively when supply is available, meaning they all participate in a smart grid, because the high load (one Japanese estimate was over 7 GW for half the cars in Kanto)[citation needed] simply cannot be managed on an analog grid, lest "The uncoordinated charging can result in creation of a new peak-load" (ibid).
Rocky Mountain Institute in 2015 listed the applications of such distributed networks of batteries[30] as (for "ISOs / RTOs") including "energy storage can bid into wholesale electricity markets" or for utility services including: RMI claimed "batteries can provide these services more reliably and at a lower cost than the technology that currently provides a majority of them thermal power plants (see above re coal and gas)", and also that "storage systems installed behind the customer meter can be dispatched to provide deferral or adequacy services to utilities", such as: