To determine the optimal utilization of hybrid bonds relative to the 15% equity credit cap, we evaluate the company's financial position at the end of 2022:

1.  **Capital Structure Analysis (as of 2023-01-01):**
    *   **Equity:** 3,644,700,000 EUR
    *   **Financial Liabilities (Noncurrent + Current):** 5,689,900,000 + 650,100,000 = 6,340,000,000 EUR
    *   **Total Adjusted Capital (Debt + Equity):** 9,984,700,000 EUR
    *   **S&P Hybrid Cap (15% of Adjusted Capital):** 0.15 * 9,984,700,000 = 1,497,705,000 EUR

2.  **Financial Context:**
    *   The company saw a significant increase in financial liabilities from the previous year (Noncurrent Financial Liabilities rose from 3.7 billion to 5.7 billion EUR).
    *   The current interest rate environment shows a sharp increase in swap rates (e.g., 10Y swap at 1.927% in 2022 vs 0.053% in 2021).
    *   While the company has a strong liquidity position (Cash and Cash Equivalents increased to 1.94 billion EUR), the cost of debt has risen significantly, increasing the attractiveness of capital instruments that provide equity-like characteristics to optimize ratings and manage leverage.
    *   Given the substantial reliance on noncurrent debt and the need to maintain creditworthiness while managing high financing costs (Finance costs were 217.2 million EUR), utilizing the full capacity for hybrid equity credit is a standard strategic move for capital-intensive utility groups like Hera S.P.A. to prevent rating deterioration without violating the S&P threshold.

3.  **Conclusion:**
    *   To maximize financial flexibility and support the company’s capital-intensive investments (PP&E of 1.98 billion and Intangible assets of 4.41 billion), the company should utilize the full limit allowed by S&P Global Ratings.

<answer>100%</answer>