What Is Dispatchability, and How Is It Used Today?
Summer peak demand for electricity in the United States is expected to rise by 122 GW over the next 10 years, representing a nearly 16 percent increase from current levels. Even though load growth is a feature, not a bug, of the energy transition, utilities must pursue thoughtful and proactive planning to ensure that they can meet growing energy demand not just reliably, but affordably. It is in this context that a growing number of planners, politicians, and pundits are centering on dispatchability as the key to keeping the lights on. In doing so, however, they risk missing the forest for the trees, losing sight of cleaner and more-cost effective options that can support what really matters — system reliability.
Dispatchability reflects the ability of a resource to turn on or off, or increase or decrease its power output, on demand during normal operating conditions. The concept of dispatchability has featured prominently in discussions about power generation, including power plant retirements and new resource additions in anticipation of growing demand. Even though non-emitting resources such as renewables paired with battery storage can be dispatchable, calls for more dispatchable resources are often coded language for new natural gas plants, or for keeping uneconomic coal plants on line.
At times, both federal and state decision makers have zeroed in on dispatchability as the most important attribute for adding new electricity-generating resources to the grid and ensuring the grid can reliably serve electricity customers. For example, a Federal Energy Regulatory Commission (FERC) commissioner recently expressed his concern that dispatchable resources are being retired too quickly. Similar concerns have prompted proposed legislation, called the US Grid Power Act, that would allow fast-track reviews of dispatchable resources in the interconnection queue.
At the state level, a new law in Kentucky keeps dispatchable resources on line, regardless of economic performance. Similarly, a loan program in Texas designed to enhance grid reliability was structured such that only dispatchable resources would qualify.
Such language and legislation might lead one to conclude that dispatchability is essential for the continued reliable operation of the electric power sector. The reality is that dispatchability, on its own, is an insufficient and potentially misleading criterion for evaluating new resource additions. In fact, so-called “dispatchable” resources can and have failed to dispatch, leading to major outages. A disproportionate focus on the dispatchability of specific generation resources risks steering discussions away from what really matters — achieving and maintaining a reliable and affordable power system.
Why Reliability Requires More Than Just Dispatchability
We cannot solve for a 21st-century grid with 20th-century solutions. Relying on dispatchability alone is like relying on print newspaper ads for marketing, when we have a suite of digital marketing channels, in addition to newspapers, at our fingertips.
While dispatchability refers to operators’ ability to control a resource’s output, the reliability of a resource reflects its ability to generate electricity and support the grid during normal operating conditions and periods of grid risk, such as during an extreme storm or a period of peak demand. During such high-risk periods, dispatchable resources may not be available, due to issues like mechanical failures or insufficient fuel supply.
Ultimately, what matters most for customers isn’t dispatchability, or even resource-level reliability, but rather system reliability — the grid’s ability to meet consumer demand during normal operating conditions and periods of grid risk. Critically, system reliability can be supported by both “dispatchable” and “intermittent” resources, along with the underlying transmission network.
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