This study presents a detailed analysis of energy consumption in supermarkets, combining field measurement and parametric analysis to optimize efficiency using theoretical modelling. Using a 6780 m² supermarket near Stockholm as a case study, advanced technologies were integrated, including CO2 refrigeration cycle with heat recovery, ground boreholes as thermal storage, LED lighting, PV panels, and optimized ventilation. Energy data were collected through sub-metering, synchronized with temperature and pressure measurements of the refrigeration cycle, and analysed to validate EnergyPlus/Python simulations. Simulations used for evaluating refrigeration demands, HVAC loads, and overall energy consumption. Results show a 60 % reduction in energy use intensity comparing to a basic-reference supermarket, achieving 140 kWh/m² annually. Key findings include a 17 % reduction in electricity use with LED lighting, a 55 % decrease in medium-temperature (MT) cabinets’ refrigeration demand and a 64 % drop in space heating demand due by adding doors in the MT cabinets. Integrating heat recovery into the CO2 refrigeration system reduces energy consumption by an additional 7 %. Thermal storage further improved system efficiency by optimizing subcooling, while photovoltaic panels reduce grid dependency by 29 %. These results demonstrate the potential of modern technologies to improve energy performance and sustainability in the retail sector, offering actionable insights for designers and policymakers.