One bond deal created an entirely new market category, and then tested what happens when targets are missed.
In September 2019, Italian energy giant ENEL issued the world’s first major corporate sustainability-linked bond, creating an entirely new market category. When ENEL later missed targets and triggered coupon step-ups on $11 billion of bonds, the case became both the SLB market’s origin story and its defining test of credibility.
The ENEL case crystallises the central tension in sustainability-linked finance: should the market reward the existence of accountability mechanisms, or should it demand that those mechanisms actually change behaviour? ENEL’s step-ups worked as designed, but if the penalty is small enough to absorb without altering corporate strategy, the instrument risks becoming a sophisticated form of greenwashing rather than a driver of real transition.
Supporters argue that the SLB structure is inherently superior to traditional green bonds because it ties financing to outcomes, not inputs. Even when targets are missed, the step-up creates transparency, investors and the public can see exactly where the issuer fell short. Perfection is not the standard; accountability is. And the market is self-correcting: future SLBs will face pressure to set more ambitious targets and larger penalties precisely because ENEL’s experience demonstrated the cost of insufficient rigour.
Critics counter that a 25 basis point penalty on a multi-billion-dollar bond programme is trivial relative to the issuer’s overall cost of capital. If the financial consequence of missing a climate target is negligible, the target is decorative, not binding. The SLB market’s credibility ultimately depends on whether issuers set targets that are genuinely difficult to meet, and whether the consequences of failure are large enough to make boards uncomfortable. ENEL’s case suggests the market has not yet reached that threshold.
When ENEL triggered coupon step-ups on approximately $11 billion of bonds after missing sustainability targets, critics called it a failure. But the step-up mechanism was designed precisely for this scenario: investors received higher returns as compensation for underperformance, and ENEL paid a financial price. The question was not whether accountability worked, but whether 25 basis points was enough of a deterrent.