A Structural Invariant in Zero-Cost Co-Production Systems: Empirical Evidence Across Five Physical Domains

Structural energy surplus — hydroelectric spillage, wind curtailment, industrial waste heat — commands near-zero market value. GPU compute converts electrons into bits at Mₙet = 1, 066 €/MWh (γ = 0. 875), set by the global compute market independently of physical origin. The gross value multiplier Φ = Mₙet/p₀ holds across five independent surplus domains and 36 of 38 hardware × infrastructure combinations (Φₒps ∈ 8. 9×, 28×; Φcan ∈ 11×, 105× at γ = 1): a structural consequence of global bit pricing against local electron stranding. We identify four conditions (A1–A4) and prove the Intertemporal Synergy Theorem (IST): any A1–A4 system exhibits Σ (t) > 1 strictly increasing, divergent NPV when shadow-price growth exceeds the discount rate, and strictly convex delay cost. We derive a closed-form occupancy boundary ηₘin (p₀) and a two-step screening criterion (Φ ≥ 10×, 1 h). Calibrated at Miranda do Douro M4: Σ (0) = 97. 4. Key results: ΦB = 26. 6× (canonical, η = 1) ; Φₒps = 23. 2× (operational, γ = 0. 875) ; Mₙet = 1, 221 €/MWh; payback 1. 3 yr (regime) ; IRR = 33. 4%. Companion papers: C2 Selection: https: //doi. org/10. 5281/zenodo. 19520816 C3 Atom: https: //doi. org/10. 5281/zenodo. 19520818