Glasgow-Based Campbell & Kennedy have secured their second deal with Bambergh District Council following a the completion of a "phase 1" trial.
The company was appointed by Breyer Group last month, through the LHC Procurement Framework.
It will now work on thousands of homes across both the Bamberg and neighbouring Mid Suffolk councils, as they authorities work towards the energy efficiency standards recently set by Westminster.
The project itself is the largest of its kind to be carried out in the UK, with around 2,200 panel systems to be installed over the next 15 to 18 months.
As a result, the contract is likely to net Campbell & Kennedy more than £6.5 million.
Gerry Kennedy, managing director, said he was delighted to have secured the lucrative deal.
He added: "It's a win-win as not only do the tenants benefit but also the council will recoup its investment and generate an income to benefit all ratepayers.
"Based on a resident using only 50 per cent of the electricity generated each household could save up to £150 or more per year.
"If you consider that more than 2,000 systems are being installed and that the systems will continue to generate electricity for 25 years or more, you can quickly see that the councils will create some substantial savings on behalf of their residents."
A total of 22,090 solar panels will be fitted during project, to make up the total 2,209 systems.
Each system is capable of generating 2.5 kilowatt peak (kWp) — enough to power to cover half of the average families annual requirement. Regarding the Bamberg and Mid Suffolk contract, the 2,209 properties will make combined savings of approximately £300,000 per year, amounting to around £12.9m over 20 years.
While the contract is already a major boost for the Scottish firm, the prospect of further deals has already been discussed.
Councillor Jennie Jenkins, leader of Babergh District Council, said they were already looking at ways to extend the scheme.
Babergh is a district on the southern tip of Suffolk with a population roughly the size of the Stirling council area.