Many banks are keen to show they are considering their environmental impact as savers become increasingly conscious about the environmental impact of their money and investments.

However, almost seven in 10 (69%) people surveyed by Which? said they would not know how to find information about a bank’s green credentials, making it difficult to compare providers.

To help consumers understand how sustainable different potential homes are for their savings, Which? worked with Ethical Consumer to rate 18 savings providers, including building societies and high-street banks, on their green credentials.

Each provider was assessed and awarded points based on publicly available information across four categories – environmental reporting, carbon management and reporting, transparency and the company’s ethos, with a maximum possible score of 100.

The most sustainable savings providers

Triodos Bank emerged as the most sustainable savings provider with an impressive score of 92 out of 100. The bank achieved top scores for its carbon reporting and management as well as ethical lending policies.

Ecology Building Society and Nationwide Building Society were in joint second place, both scoring 90 out of 100.

Ecology Building Society impressed researchers with its transparency, prominently disclosing its lending and investment activities on its website. Nationwide was the first UK building society to report on the carbon emissions of all the housing it lends on. It has withdrawn from commercial lending, which rules out fossil fuel investment.

Leeds Building Society, Skipton Building Society and the Co-operative Bank were rated fourth, fifth and sixth respectively. The Co-op was the highest scorer (58 out of 100) out of the high street banks. It scored well due to its target to send no waste to landfills, however it lost points as its sustainability report did not detail how it helps customers address their environmental impact.

The worst savings providers for sustainability

There was a stark difference between the top three sustainable saving providers and most of the high-street banks, which finished in the middle or at the bottom of the table with less impressive scores.

NatWest scored 54 out of 100, Lloyds Banking Group 52, HSBC 44, Barclays 41, and Santander 35. While they all performed well in the environmental category, their policies rarely included a complete ban on fossil fuel investment.

Barclays’ climate-related financial disclosures showed the bank had investments in aviation, coal mining and oil and gas.

Gatehouse Bank is a Sharia-compliant bank which means it does not invest in the gambling, alcohol or arms industries. However, it only scored 27 out of 100 as it was not transparent about the industries it does invest in. Researchers also could not find any evidence of publicly available emissions reporting, despite the bank offering a range of green savings accounts and individual savings accounts (ISAs).

Other smaller ‘challenger’ banks such as Atom Bank (11/100) also received poor scores due to lack of information, even though their small size may reduce their relative impact upon the environment.

Does sustainability impact interest rates?

Which? also analysed interest rates offered by all 18 providers and found that making greener choices does not need to cost savers.

The high street banks that finished in the middle of the table had the lowest interest rates, while some building societies and specialist banks offered competitive rates.

Jenny Ross, Which? Money editor, said: “It can be incredibly difficult for consumers to gauge how sustainable a product or company is, but when it comes to savings providers our research shows building societies and specialist banks are doing a better job on sustainability and transparency, compared to high street banks.

“While interest rates are often the deciding factor when choosing a savings provider, we know some consumers would consider moving their money if they found it was invested in industries that harmed the environment. Providers must be more transparent to help consumers compare and make informed choices.”