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 M_net = 1,066 €/MWh (γ = 0.875), set by the global compute market independently of physical origin. The gross value multiplier Φ = M_net/p_0 holds across five independent surplus domains and 36 of 38 hardware × infrastructure combinations (Φ_ops ∈ [8.9×, 28×]; Φ_can ∈ [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 η_min(p_0) and a two-step screening criterion (Φ ≥ 10×, 1 h). Calibrated at Miranda do Douro M4: Σ(0) = 97.4. Key results: Φ_B = 26.6× (canonical, η = 1); Φ_ops = 23.2× (operational, γ = 0.875); M_net = 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