Navigating energy performance certification is critical for UK commercial property compliance. Energy Performance Certificates (EPCs) evaluate theoretical efficiency based on building design, whilst Display Energy Certificates (DECs) measure actual consumption using utility data. EPCs are required for property transactions; DECs are mandatory for public buildings over 250m². With MEES Phase 2 requiring EPC B ratings from April 2027, understanding certificate differences is essential for landlords, asset managers, and facilities managers. This guide covers legal requirements, costs, validity periods, strategic importance, and practical steps to optimise both certifications for compliance and cost savings in commercial property portfolios.