Roads as solar energy collector

Dutch Company Siphoning Heat from Asphalt for Energy Uses from TreeHugger reports how a Dutch civil engineering company can collect heat from asphalt covered road, store in deep underground aquifers and later retrieve.

Originally a system erected to reduce road maintenance costs, Ooms' technology consists of a network of flexible pipes held in place by a grid and covered over by asphalt - which helps magnify solar heat. Heated water coursing through the pipes is pumped deep underground into aquifers; it can then be retrieved, even months later, to keep the road ice-free during the winter. Alternatively, the system can pump cold water from a separate reservoir to cool homes or office buildings in the summer.

Using underground aquifers as a heat buffer, cooled during winter months and used for cooling in summer (hereby warming aquifers and storing the heat for winter warming need)! How clever!

Question: If household use, how large is the heat buffer needed to maintain a Melbourne home comfortable year round?