Firm power

Firm power is electricity supply that a generator or utility contractually guarantees to deliver on demand, regardless of weather or fuel conditions, as opposed to non-firm or intermittent supply that can be curtailed. Combined-cycle gas plants, nuclear, hydro with storage, and grid-connected baseload contracts are typically sold as firm; standalone wind and solar are non-firm because output depends on conditions outside the generator's control. Data centers, especially hyperscale and AI campuses running near-continuous IT load, generally require firm power to meet uptime SLAs, which is why renewable PPAs for data centers are usually paired with storage, gas peakers or grid balancing to convert intermittent generation into an effectively firm supply — a process the industry calls "firming." Utilities and grid operators price firm power at a premium over non-firm energy, and interconnection queues increasingly distinguish firm capacity commitments from energy-only or curtailable contracts when allocating scarce substation capacity to new data center loads.