Parts of Inverness have been identified as potential locations for large heating networks in the future.
Highland Council, along with Scotland's other local authorities, have been asked by the Scottish government to come up with strategies to improve energy efficiency.
Heat networks involve distributing energy from a central source, often using underground pipes to carry hot water.
Inverness' west bank of the River Ness, the city centre, Longman and Raigmore areas could have networks, according to a report to Highland Council's climate change committee.
Properties would be warmed by one or more systems that extract heat from air, water or underground.
Biomass, hydrogen and facilities that draw thermal energy from warm water households flush down drains could also be used.
Many of the properties are currently heated by mains gas.
