Beyond Efficiency: A Unified Survival–Conversion Law for Real-World Energy Systems

Classical energy efficiency metrics, defined as the ratio of useful output to supplied input, systematically overestimate the usable energy delivered by real systems operating under natural and engineered conditions. Across an exceptionally wide range of scales—spanning cellular metabolism, organismal growth, ecosystem productivity, photovoltaic power plants, electric transportation, aerospace systems, and large-scale data centers—measured field performance consistently falls far below laboratory efficiencies and theoretical upper bounds. This discrepancy persists despite decades of technological optimization and cannot be resolved by improvements in component-level efficiency alone. Here, we introduce a Unified Energy Survival–Conversion Framework that reformulates useful energy production as a survival-limited, non-equilibrium thermodynamic process, rather than an idealized efficiency problem. We define an energy survival factor, Ψ=AE/TE+ε, where AE denotes absorbed energy successfully retained within system boundaries, TE represents transport, leakage, and environmental dissipation losses, and ε captures irreducible entropy production mandated by the second law of thermodynamics. Unlike conventional efficiency ratios, Ψ explicitly quantifies the probability that absorbed energy survives competing loss channels long enough to remain available for productive conversion. By coupling this survival factor with an internal conversion capacity term Cint, which represents finite reaction, transport, structural, and throughput constraints, we derive a universal performance law: Euseful=Ein×Ψ×Cint This formulation decomposes usable energy output into independently measurable survival and conversion components, providing physical transparency absent from classical efficiency metrics. Application of the framework to empirical data across biological and engineered systems demonstrates that observed performance ceilings—typically ~1–3% for ecosystem-scale photosynthesis, ~15–22% for utility-scale photovoltaics, ~60–80% for electric drivetrains, and