Hotels are among the top energy consumers in the non-residential sector, yet significant waste offers substantial opportunities for improvement—essential for meeting the EU’s nearly zero-energy building (nZEB) targets and climate-neutral goals by 2050. This study uses a typical four-star hotel as a case study to establish cost-optimal nZEB performance indicators across three European cities: Faro, London, and Athens.

Following a detailed energy audit and model calibration using building energy simulation, the research evaluates the best retrofit packages, demonstrating that significant energy savings and nZEB levels are technically and economically achievable for refurbished hotels across diverse climatic contexts.

The hotel sector is among the most energy- and resource-intensive areas of tourism, making the optimisation of building performance – particularly in the 4- and 5-star segment – essential to achieving the European Union’s 2020 and 2030 nearly zero-energy building (nZEB) targets and the long-term goals of Portugal’s Low Carbon Roadmap 2050. Using a typical four-star Portuguese hotel as a case study, a comprehensive energy audit and detailed modelling in DesignBuilder/EnergyPlus were conducted to evaluate energy use and validate realistic performance benchmarks.

By testing a range of integrated interventions—combining passive design strategies, active technical solutions, and renewable energy systems—the study defined cost-optimal pathways to meet minimum energy performance requirements and provided novel indicators to quantify feasible nZEB levels across the national hotel portfolio.