To determine the appropriate utilization of hybrid bonds relative to the 15% S&P equity credit cap, we must evaluate the company's financial structure and the cost of debt.

1.  **Financial Position (End of 2022):**
    *   **Equity:** 6,304,000,000 EUR
    *   **Financial Debt:** "Participaciones Preferentes Obligaciones Y Otros Valores Negociables No Corrientes" (3,101,000,000 EUR) + "Noncurrent Portion Of Noncurrent Loans Received" (2,624,000,000 EUR) + "Current Loans Received" (553,000,000 EUR) + "Participaciones Preferentes... Corrientes" (1,139,000,000 EUR) = 7,417,000,000 EUR.
    *   **Total Adjusted Capital (Debt + Equity):** 7,417,000,000 + 6,304,000,000 = 13,721,000,000 EUR.
    *   **15% Cap:** 0.15 * 13,721,000,000 = 2,058,150,000 EUR.

2.  **Contextual Analysis:**
    Acciona S.A. is heavily capital-intensive, operating primarily in infrastructure and renewable energy. The market data for 2022 shows a significant increase in the swap curves (e.g., 10Y swap at 1.927% vs 0.053% in 2021) and rising credit spreads (iBoxx EUR Non-Financial IG up to 2.295% vs 1.298% in 2021). 

3.  **Strategic Rationale:**
    As interest rates rise and the cost of conventional debt increases, hybrid bonds become an attractive financing tool for maintaining credit ratings while funding high-capex projects (evidenced by the company's high investment outflows of 2,439,000,000 EUR). Given the significant increase in the company’s "Noncurrent" debt from 2021 to 2022 (approx. 1.3 billion EUR increase) and the need to preserve cash flows for operations and capital investment, maximizing the equity credit afforded by hybrids is financially prudent to support the company’s credit profile. Since the company’s capital structure requires sustaining significant debt to fund assets, and it has already issued substantial noncurrent debt instruments, utilizing the full extent of the S&P 15% cap is the most aggressive and efficient way to manage leverage ratios while minimizing the impact on the firm's cost of capital in a rising interest rate environment.

<answer>100%</answer>