The Co-operative Bank is to increase its lending to renewables projects from £400m to £1bn.
In its latest ethical statement the bank said it would be targeting small to medium projects with a capital value of up to £25m.
In 2007, the bank ring-fenced £400m for energy-saving and renewable investments, and last year it revealed it had signed off on half of this amount.
The bank believes that financing of smaller projects is essential to the UK achieving a low carbon economy and has had considerable interest from community groups and smaller developers since the introduction of feed-in-tariffs.
To handle this increase in business, the bank has expanded its renewables operation at its Manchester headquarters and has formed a new team in Scotland.
The Co-operative Group operates both banking and retail outlets and has been carrying out a refit of its supermarkets in a bid to cut a quarter of its energy consumption by next year.
The company has installed more than 3,000 smart meters and is carrying out 700 store refits a year.
Last year, the group introduced the UK’s first 100% recycled plastic shopping basket in its food stores. Some 94,500 baskets are now in use in around 1,000 Co-operative stores, saving 66 tonnes of plastic from landfill or incineration and 66 tonnes of CO2.