Traditional SETI assumes advanced civilizations consume growing energy, producing infrared waste heat. This paper proposes intelligence density—computations per Joule—as a better measure. It argues efficiency gains can overtake computational growth δ>γ. In this new regime, civilizations process vast information while energy use stabilizes, creating thermodynamic camouflage. Examples include neuromorphic chips, ant colonies and octopus arms. Earth may reach this transition by the 2030s.