Hospitals generally have large internal heat gains in core areas from diagnostic imaging and other medical equipment. Hospitals in Scandinavia also have a building envelope with large facades and glass for daylight and outside views. These factors, combined with high ventilation airflow rates and long occupancy schedules, make hospitals the most energy intensive of all building types. Ground source heat pumps can deliver both heating and cooling to such buildings, but their cold-climate performance will be much reduced without a well-designed energy collection and storage strategy. Improper dimensioning can lead to permafrost and much reduced ground source effectiveness. The timing of heating and cooling demands can also lead to reduced effectiveness due to higher return temperatures and increased compressor work. The authors show how these challenges can be converted into a cold climate advantage through the use of a seasonal energy balancing technique and integrating hybrid heat sources into the storage strategy. The authors also define a new metric for quantifying the overall energy performance of investing in increased storage capacity at different timescales. This metric is then used in case studies of actual buildings in Norway to compare several cold-climate thermal storage and free-cooling strategies. The energy balance method allows the HVAC designer to quickly evaluate different hybridization strategies to leverage both "free-heating" from the internal heat gains and free-cooling from the target climate without the need for a detailed thermal model. This approach will help to determine the cost-effectiveness of various hybrid heat sources and storage mass, and to reduce the number of costly ground source boreholes. The approach described in this paper may have cold-climate applications to other building types with large internal process heat gains.