Tertiary basins in south-central British Columbia may be economic sources of hot water for space heating. The heat flow, 72 mW m−2 for the Penticton Tertiary outlier, and the insulating layers of volcanic sediments produce particularly high temperatures within this basin. Underneath White Lake, the temperature at the bottom of a spectacular thickness of sediments may be 90 °C. The measured porosity, approximately 5%, and the water flows observed in boreholes indicate ample fluid and apparent permeability to extract significant heat from the rocks. However, a more qualitative assessment of these parameters can only come from a thorough hydrogeologic study involving several test wells.The regional heat flow indicates that Coryell-type intrusions having a high radioactive heat generation do not form a significant proportion of the upper crust.