The Leuphana University of Lueneburg achieved the first climate-neutral energy balance for heat, electricity, cars and business trips in 2014. The chapter focuses on the energy concept as part of an integral approach towards sustainability. A simulation study was carried out to quantify the advantageous impact of a seasonal heat storage in an aquifer on the district level. With the integration of the heat storage, the share of renewable heat reaches 95% and leads to 2,400 t less CO2 emissions.