Firm generation is electricity supply that can be counted on to produce power steadily when needed, rather than only when weather or daylight allows it. Common examples include nuclear, gas, hydro with storage, and some biomass plants. In power-system planning, firm generation matters because it adds dependable capacity that helps balance demand, cover peak loads, and reduce the amount of battery storage a grid must carry.
In cyber security and critical-infrastructure defense, firm generation is relevant because resilient power systems are harder to disrupt. If an attacker targets a grid with outages, communication failures, or scheduling pressure, firm generation can provide a stable fallback while operators restore control. It is not a security control by itself, but it is a resilience control: it lowers dependence on volatile supply and can reduce the impact of cyber or physical disruption on continuity of service.