Gloucester Cathedral is currently installing up to 200 solar panels on its roof.
The renewable upgrade to the Grade I listed building will cost £100,000 and is expected to cut its energy use by 25%, saving enough power to make 2,000 cups of tea every day of the year.
The panels, which the cathedral says will be invisible from the ground, are being installed by Mypower and will provide power for a newly installed underfloor heating system.
Once the work is completed, the 1,000-year-old building will become the oldest cathedral in the UK and possibly the world to have installed a commercial-sized solar panel array on its roof.
Reverend Canon Celia Thomson said: “The installation of solar panels on this remarkable building is a historic moment. We are thrilled that our vision to become a greener Cathedral is being fulfilled and proud to make a valuable contribution to the Church of England’s Shrinking the Footprint campaign.”
More than 3,500 churches across Britain have already ditched fossil fuels for renewable energy or have registered to do so.