Residents in part of Lincolnshire have been warned to be vigilant when being approached by solar panel salesmen.
It follows an increase in companies offering North Kesteven residents solar PV panels for their homes.
The government's clean energy cashback incentive scheme has led to many salesmen cold calling, the district council said.
It added that some residents have been given misleading advice and not always offered the best deal.
The leader of the council, Councillor Marion Brighton, said: "With the introduction of the clean energy cashback scheme, there are some great benefits to installing solar PV, and some really good financial incentives, there hasn't been a better time to invest.
"We do however want to make sure that our residents are getting the best deal possible and for that reason we urge our residents to contact the Energy Saving Trust for free, impartial advice."
The scheme, also known as "feed-in tariffs", was introduced in April and offers incentives for those who install small-scale energy renewables on their homes.