Global carbon emissions have surged by 60% since 1990, presenting a pressing challenge for sustainable development. Sweden, despite significant efforts to reduce carbon emissions, still has ongoing challenges with high carbon outputs, particularly in sectors like construction, which contributes 22% to the nation's emissions. In response to this, urban developer Bonnier Fastigheter has committed to reducing its environmental footprint while enhancing property sustainability in new projects. Bonnier Fastigheter's plans for three commercial projects in Stockholm Seaport align with the EU Commission's Positive Energy District (PED) initiative, emphasizing sustainable urban development. This work will focus on the Pirhuset project as a case study, presently in the design phase. The goal is to assist the company in developing an energy-efficient and sustainable commercial building. The main objective was to achieve an Energy Performance Certificate (EPC) rating of A, corresponding to a primary energy demand of ≤ 35 kWh/m² per year. The analysis explores optimizing building properties and integrating local renewable sources. Alternative solutions involving geothermal heat pumps, rooftop solar PV, and electricity storage are evaluated for reduced emissions during operational energy usage. A life cycle cost analysis, together with environmental impact executed for this study as a recommendation and guiding the final decision on achieving Pirhuset's energy efficiency goals for the company. Building and energy system simulations were conducted using IDA-ICE. The results showed that the baseline model with optimized building properties offered the most cost-effective solution. However, in terms of environmental impact, Alternative 2, which utilizes a geothermal heat pump with boreholes and solar PV panels, proved to be the more sustainable option. For future work, a deeper analysis of this energy-sharing potential, along with the utilization of waste heat from BECCS by Stockholm Exergi, is anticipated. Exploring the synergies and technical aspects necessary for this to work would be highly interesting within sustainability urban planning.