A solar heated area comprising 50 residential units is under construction. The system includes low-temperature space heating with seasonal ground storage of solar heat. Heating is supplied by 2 400 m{sup 2} of solar collectors and individual electrical heaters for supplementary heating. During the summer part of collected heat is stored in a borehole store with 100 boreholes drilled to 65 m depth. The groundwater-filled boreholes are fitted with double U-tubes. The average temperature of the seasonal store, about 60,000 m{sup 3} of crystalline rock, varies between 30 and 45 deg. C over the year. A floor heating system designed for a supply temperature of 32 deg. C provides space heating. The system is also equipped with buffer tanks for pre-heating of domestic hot water. The collectors will have favourable working conditions but the store is rather small and the estimated heat loss from the heat store is about 40% of collected solar heat. The average solar fraction is estimated to 70% and the resulting total heating cost is estimated to about 1 000 SEK/MWh ({approx}120{open_square}/MWh).