This book constitutes the proceedings of the First Nordic Energy Informatics Academy Conference, Nordic EIA 2025, which took place in Stockholm, Sweden, in August 2025. The 43 full papers and 8 short papers accepted were carefully reviewed and selected from 65 submissions. They were organized in topical sections as follows: Part I: Energy Forecasting and Intelligent Control Systems; District HEating, Thermal Systems, and Retrofit Strategies; Building Simulation, Urban Energy, and Environmental Sensing; Industrial Process Efficiency and Biomass Utlilzation; Energy Informatics for Electric Vehicles and Mobility Systems; Multi-Agent Systems and Local Market Coordination; Part II: Policy, Metrics, and Infrastructure Performance; Smart Buliding Systems and Semantic Data Integration; Prosumer Optimization and Energy Storage in Local Energy Communities, Grid-Oriented AI, Simulation, and Resilience; Non-Intrusive Load Monitoring and Data Competitions.