Prison chiefs have gained permission to install solar panels on the roof of HMP Perth.
The energy-saving system will feed directly into the Edinburgh Road establishment’s power supply and is expected to slash electricity bills.
The Scottish Prison Service said the £41,200 panels will reduce greenhouse gas emissions by 53 tonnes each year.
Similar projects are being carried out at HMP Low Moss and the Polmont young offenders facility.
Perth and Kinross Council has now granted planning permission for the rooftop installation.
In a report to officials, planning officer Andrew Baxter said: “The solar panels are to be installed on the east elevation of a recent store building, which has no architectural merit.
“The visual impact of the solar panels upon the setting of the category A-listed building will not be significant and this view is shared by the conservation officer.”
Clydebank firm Campbell and Kennedy has secured contracts for the work at all three jails.
The company’s head of energy, Jason Lowey, said: “Given the amount of electricity that is used at each of these sites, the installs will be a great way to reduce costs, as well as help the environment.”
This year the Scottish Government launched a consultation that proposes the removal of planning permission requirements for commercial rooftop solar installs.
It is intended to help stimulate the technology’s roll-out across the country.
A spokesman for the prison service said: “The SPS is committed to incorporating renewable energy across our establishments.