LEARN / GLOSSARY
Firm power
Electricity a system can count on being available when it is needed, as opposed to energy produced when conditions permit. The distinction is what a continuously running factory actually buys.
Definition
Firm power is electricity a system can count on being available when it is needed, as distinct from energy that is produced when conditions permit. A resource is firm to the degree that its output can be scheduled and sustained through the hours the system is most stressed.
Why the dictionary version is insufficient
Describing firm power as reliable power invites the reader to treat firmness as a property of a machine. Firmness behaves more like a property of a portfolio evaluated under specified conditions. A generator with fuel stored on site is firm during a still, cold week in a way that the same nameplate rating of wind capacity is not, and the difference appears only in the hours that matter.
Why it matters for capacity
A production line running continuously must be served in every hour, including the ones when generation is scarcest, so a plant evaluates firmness rather than annual energy. NERC has reported that fossil-fired retirements reduce the amount of generation with fuel on site, which affects the system’s ability to respond to demand spikes, while most resources in development over the next five years are inverter-based and weather-dependent.
Institute analysisAnnual energy totals and firm capacity are frequently reported as though they were the same quantity. For industrial siting they are not close, because a factory buys availability in specific hours rather than kilowatt-hours in aggregate.
Related terms
Interconnection queue · Capacity factor · Nameplate capacity
Appears in
Why Reindustrialization Requires More Electricity
Read next
Why Reindustrialization Requires More Electricity