The plan forms one part of a £10 million boost to climate projects across the West of England region.
Old coal mines naturally flood with water which is heated by geothermal processes, and the water can then be piped above ground for heating.
This is a climate-friendly alternative to using traditional gas boilers, which burn fossil fuels and emit carbon emissions and other greenhouse gases.
The plan was welcomed by West of England metro mayor Dan Norris, who said it was “ironic” that coal mines could be one solution to climate change. The plan will be funded by Mr Norris’s green recovery fund, which is now increasing from £50 million to £60 million.
The £10 million boost to the green recovery fund was agreed by the region’s political leaders at a WECA meeting on Friday, March 17.
Other projects paid for by the fund include planting thousands of trees and helping to support struggling bees.
Mr Norris said: “This is the biggest challenge we face as a region, as a nation and as a planet. We’re investing in things like planting trees, creating green jobs and supporting pollinator projects to make sure our region is the UK’s bee and pollinator capital in the future.
“I can’t think of anything that would be more fantastic than to think what had contributed to carbon dioxide emissions over hundreds of years was then able to turn around and reduce them. There’s a kind of irony but also an important purpose there.”
The heat from coal mines project is being led by South Gloucestershire Council. The next stage is now to see how dated records of mines match up with the reality underground, as well as to assess the scale of demand for using the renewable and clean source of heat.
Council leader Toby Savage said: “We’re exploring how our coal mining heritage can sustainably help to meet the region’s future renewable heating and cooling needs.
“We have extensive mining heritage in parts of the district — in Kingswood, Mangotsfield, Coalpit Heath and Westerleigh — with over 40 coal seams and over 1,000 different mine entrances.”