Out-of-distribution (OOD) detection is crucial for machine learning models deployed in open-world environments. However, existing methods often struggle with model over-confidence or rely heavily on empirical energy value estimation, limiting their scalability and generalizability. This paper introduces DEBO (Dual Energy-Based Model for Out-of-distribution Detection), a novel approach that addresses these limitations through an innovative dual classifier architecture and a unified energy-based objective function. DEBO enhances the standard classification framework by integrating a dual-purpose output space within a single classifier. The primary component classifies in-distribution (ID) data conventionally, while the secondary component captures open-world information and estimates uncertainty. Our method overcomes the dependence of traditional energy model-based OOD detection methods on empirical energy estimation while maintaining theoretical guarantees. Theoretical analysis demonstrates that DEBO promotes low energy and high confidence for ID data, while simultaneously inducing higher energy and decreased confidence for OOD samples. Extensive experiments conducted on benchmark datasets reveal that DEBO achieves state-of-the-art OOD detection performance while maintaining comparable classification accuracy on ID data.