Heat pumps are seen as the predominant future heating system in many scenarios. However, with increasing integration of heat pumps sufficient heat sources can be a major obstacle, in particular at higher heating capacities and in existing buildings. The paper investigates two strategies to overcome limitations of the most common individual heat sources outdoor air and ground by the integration of two or more heat sources in order to enable a monovalent heat pump operation. By an integration of the ground for peak load coverage and air as base load the borehole heat exchanger field can be notably downsized, overcoming space limitations for the drilling and noise limitations due to a downsized air source. Compared to the individual air source the performance can be increased, while the system costs can be kept. Also the second strategy of the regeneration of the ground source allows for much smaller borehole fields, and the regeneration source can be refunded by cost savings due to a reduced total borehole length. Thus, performed simulations confirm that heat source integration has the potential to overcome limitations of individual heat sources while exploiting performance and cost benefits due to synergies between the sources.