This year Verizon, the American telecoms group, embarked on a $1bn experiment: in February it became the first telecoms company in the US to issue a “green” bond, or a security that raises funds for sustainable business.

You might have thought this exercise would incur some cost for Verizon’s treasurers, given that green finance has traditionally been a cumbersome endeavour. Not so. Verizon’s $1bn green bond attracted such frenzied investor demand that it was eight times oversubscribed, making it the most popular security Verizon has ever sold. Indeed, funding costs were slightly “cheaper than a brown bond [or normal security]”, says Jonathan Fine of Goldman Sachs, an underwriter. That is remarkable.

Just a lucky accident? Perhaps. Verizon benefited from being one of the first such corporate issuers. However, the rest of the market is taking note of this attractive pricing. “We expect to see more issuers tapping into the green bond market,” predicts another underwriter, Andrew Karp of Bank of America Merrill Lynch.