LEARN / REINDUSTRIALIZATION
Fuel and Storage
Installed capacity is a statement about machines. Whether those machines can run for the hours a system needs them is a statement about fuel arrangements and storage duration, and the two questions come apart precisely during the events that cause outages.
Key points
- A generator without deliverable fuel is capacity on paper and not on the system.
- Natural gas plants generally hold no fuel on site and depend on pipeline delivery in the same hours that heating demand peaks.
- NERC reports that fossil retirements reduce the amount of generation with fuel stored on site, which affects the ability to respond to demand spikes.
- Battery storage is duration-limited. A four-hour battery is firm for four hours and contributes nothing in hour five.
- Most resource adequacy constructs were built around peak hours rather than multi-day events, which is where the recent failures have occurred.
Fuel on site, and fuel on order
Generators divide usefully by where their fuel sits. A coal plant holds a pile in the yard. A nuclear plant holds a core for many months. An oil-fired unit holds tanks. A natural gas plant typically holds nothing, and runs on gas delivered through a pipeline in the hour it is needed.
In ordinary conditions that arrangement is efficient. During a severe winter event it becomes the system’s exposure, because the same cold that drives electricity demand drives heating demand on the same pipelines, and firm transportation contracts for heating customers rank ahead of interruptible service for generators. Wellhead freeze-offs reduce supply at the same moment.
NERC has identified the trend directly, noting that fossil-fired retirements reduce the amount of generation with fuel on site and that this affects the system’s ability to respond to demand spikes. That is a statement about fuel security rather than about megawatts.
Measurement noteInstalled capacity, accredited capacity and deliverable energy are three different quantities, and fuel arrangements separate the second from the third. A gas fleet with interruptible transportation can hold full accreditation under a method calibrated on historical availability and still be undeliverable in the conditions that method never observed.
Storage is duration, not capacity
Battery storage is reported in megawatts, which invites comparison with a generator, and the comparison misleads. A battery is defined by two numbers: how fast it can discharge and for how long. A 100 MW four-hour system delivers 100 MW for four hours and then nothing until it recharges.
That makes storage extremely effective against the failure mode most systems were designed around, a single evening peak, and much weaker against the failure mode that has caused recent large outages, a multi-day weather event across a wide area. Charging is also part of the problem: a battery that cannot recharge during a sustained event contributes once.
Institute analysisAccreditation methods increasingly capture duration limits for storage, and fuel deliverability for gas is captured much less consistently. The result is that the resource whose limits are best modelled is storage, while the resource carrying the largest untested exposure is the one that supplies 40 percent of American electricity. That asymmetry is a modelling artefact rather than a physical fact.
What this means for an industrial site
A facility running continuously is exposed to exactly the events these arrangements fail against. The practical questions for a site are whether the serving region depends heavily on just-in-time gas during winter, what storage duration is installed behind it, and whether the facility has any on-site generation or process flexibility of its own.
For processes that cannot tolerate interruption, the answer has increasingly been to build behind the meter, which converts a reliability question into a capital question and moves the facility outside the datasets that track grid connection.
Common misconceptions
That megawatts of storage and megawatts of generation are comparable. Storage is bounded by duration and by the ability to recharge. Generation is bounded by fuel.
That gas is dispatchable without qualification. It is dispatchable when fuel is deliverable. Firm transportation, dual-fuel capability and on-site storage are what convert the rating into availability.
That reserve margins capture fuel risk. Most were built around peak-hour adequacy and represent multi-day fuel interruption weakly or not at all.
What the evidence says, and where it is contested
ContestedHow much firm fuel arrangement should be required is disputed, and the disagreement is about who pays for insurance against rare events. One position holds that generators should be required to hold firm transportation, dual-fuel capability or on-site storage, and that the cost is small against the cost of a multi-day outage. A second holds that such requirements are paid for continuously to protect against events that occur every several years, that consumers bear the cost, and that demand-side flexibility and storage can cover the same risk more cheaply. Both are arguing about the value of avoided outages, which is estimated rather than observed.
Related Institute research
Firm Power and Why It Matters
What a system can count on in the hours that matter.
The Generation Mix
What the fleet is composed of.
Why Supply Is Not Keeping Pace
Why nameplate additions and accredited additions differ.
Sources
- North American Electric Reliability Corporation, 2025 Long-Term Reliability Assessment. nerc.com
- U.S. Energy Information Administration, Electricity generation, capacity, and sales. eia.gov
- U.S. Energy Information Administration, Hourly Electric Grid Monitor. eia.gov
- U.S. Department of Energy, The Supply Chain Crisis Facing the Nation’s Electric Grid, December 2022. energy.gov
Reference entry maintained by the Institute for American Manufacturing & Technology. Figures are drawn from primary sources and cited above. Where the Institute states a position rather than a finding, it is marked as such.