To determine the optimal extent to which EDP, S.A. should utilize hybrid bonds relative to the S&P Global Ratings' 15% cap on total adjusted capital, we evaluate the company's capital structure needs and its sector profile. 

EDP is a major player in the capital-intensive utilities sector, heavily involved in electricity generation, transmission, and distribution, as well as an ongoing transition towards renewable energy. Capital expenditures in this industry are massive, requiring substantial funding. At the same time, maintaining a strong investment-grade credit rating is critical for utilities to keep their overall cost of debt manageable. 

Under S&P guidelines, hybrid bonds can receive up to 50% equity credit (up to a limit where hybrids constitute 15% of total adjusted capital). By issuing hybrid bonds, EDP can bolster its equity base from a rating agency perspective without diluting existing shareholders, preserving its credit metrics. Even with the rising sub-senior delta and swap rates observed in 2022, the strategic benefit of protecting the credit rating and funding the energy transition makes maximizing the hybrid bucket highly advantageous. Therefore, utilities like EDP conventionally max out their hybrid issuance capacity to optimize their Weighted Average Cost of Capital (WACC) and defend their credit ratings.

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