This paper proposes an economic improved-uniqueness reliable reconfigurable ring oscillator physical unclonable function (ERRO PUF) for IoT and hardware security. ERRO PUF reduces area overhead and power consumption, improves system design reusability, and reduces hardware resources utilization. It generates more CRPs with considerably less hardware resources, improves hardware efficiency of the PUF design, and achieves better performance with significantly less hardware resources requirement when compared with state-of-the-art configurable RO PUFs. ERRO PUF results show that the proposed model is suitable for enhancing a lightweight hardware security system and eliminating the need for trading security with area and power reduction.