Heat the Streets is the UK’s pioneering high-density ground source heat pump (GSHP) project, partly funded by the European Regional Development Fund (ERDF). It was delivered in rural Cornwall, UK.With the progress towards the UK’s net-zero targets for domestic heating being significantly behind schedule, the project demonstrated that GSHPs can be retrofitted to domestic properties without the need for a ‘fabric-first’ approach, at scale, and with no upfront cost to the customer. Heat the Streets demonstrated how mass, street-by-street rollout of GSHPs in a coordinated networked fashion can be facilitated. During the project the world’s first in-road retrofit of a shared ground array was successfully granted planning permission and installed. 100+ properties received GSHP’s across new build properties, private and social housing retrofits.