A renewable energy system used to heat some council houses in Lochaber can be more expensive to run than older heaters, a councillor has claimed.
Andrew Baxter said tenants had told him that the new air source pump heating was less efficient than electric storage heaters.
A tenant in Strontian also had to wait a week for an engineer to fix a problem, the councillor added.
Highland Council said help was available on operating the system.
Air source systems absorb heat from the outside air, which is used to warm radiators and under-floor heating.
Mr Baxter, a councillor for Fort William and Ardnamurchan, told BBC Alba some tenants now had higher energy bills than in the past.
He said: "The main concern I have is that the council has been busy spending lots of money on replacing heating systems with air source pump heating systems on the basis it is for more efficient and cheaper for tenants to run."
Mr Baxter added that the system was being serviced and maintained by engineers who had to travel from central Scotland.
Highland Council said independent advice was available to tenants on the efficient operation of the system.
It said the system was being maintained by the company that installed the heating under a five-year warranty.
However, the local authority plans to train up its own engineers to eventually take over the servicing and repairs.