Homes in Lewisham, Greenwich, Bexley and north Kent could be heated by the Thames, according to the government.
A new 'heat map' shows the river - along with around 40 others nationwide - could provide large-scale renewable heating supplies through water source heat pumps, instead of traditional gas-fired or electric heating.
Water source heat pumps operate by taking heat from the water and feeding it into local heat networks or single buildings, providing a low-carbon source of renewable heat.
Energy and Climate Change Secretary Ed Davey said: "It sounds like magic but using proven technology we can now extract some of the heat in our rivers and estuaries and use that energy to heat our homes and offices.
"I want to help communities across England use our waterways for this renewable heat and this new map is designed to help communities, councils and developers identify the most promising opportunities.
"If we can succeed on the large scale, it would cut Britain’s import bill and boost our home-grown supplies of clean, secure energy."