Classical energy efficiency metrics often overestimate real-world system performance because theyassume a single-stage conversion of input energy into useful output. In practice, energy must passthrough multiple stages of absorption, transport, regulation, and transformation, each subject toirreversible losses governed by thermodynamic constraints. This study introduces a universal survival–conversion framework that replaces idealized efficiency with a physically grounded formulation of usefulenergy production. The governing law is expressed as Euseful = Ein × Ψ × Cint, where Ein representssupplied energy, Ψ denotes the energy survival factor defined as Ψ = AE / (TE + ε), and Cint representsinternal conversion capacity. The survival factor quantifies the fraction of absorbed energy that persistsagainst transport losses and entropy-driven dissipation, while conversion capacity represents thesystem’s throughput limits. The framework applies consistently across biological metabolism, aerospacesystems, transportation technologies, renewable energy infrastructure, computing systems, andcommunication networks. The proposed law provides a unified thermodynamic explanation forperformance limits observed across both Earth-based and space technologies. Please check the attachment for details