Load shedding (loadshedding) is a way to distribute demand for electrical power across multiple power sources. Load shedding is used to relieve stress on a primary energy source when demand for electricity is greater than the primary power source can supply.
Most buildings, including data centers, purchase electrical power from a utility provider. To reduce the cost of power, while also ensuring continuous operation, a building operator may negotiate an agreement with the power provider to voluntarily load shed on a pre-scheduled or on-demand basis. During load shedding events, the building draws power from its secondary source(s) rather than from the utility. A typical secondary source is on-site diesel generators, or on-site or contracted solar photovoltaics or wind-based renewable power.
Many utilities' load management programs offer cost incentives for building operators to voluntarily load shed during peak usage periods. Load management programs are a good option for energy-intensive building operations that also have high-quality power distribution control and secondary power sources, such as a data center. To prevent disruption to the systems in the building, the operator can rely on uninterruptible power supply systems and power distribution units that moderate the flow of electricity to sensitive equipment. Small to mid-sized businesses and residential buildings with back-up power generation may also be candidates for load management programs. Environmental protection bodies define and regulate load shedding as non-emergency use of non-primary power in countries such as the U.S.
Power customers may experience involuntary load shedding when a utility electrical provider lowers or stops electricity distribution across the coverage area for a short period of time; this type of load shedding is commonly referred to as a rolling blackout. Brownouts, another type of involuntary load shedding, are caused by the power supplier lowering voltage distribution during peak usage times to balance supply and demand.