To assess the appropriate level of hybrid bond issuance for A2A Energia S.p.A. (or the broader A2A Group context provided by the report), we evaluate the financial position as of December 31, 2022:

1.  **Financial Position and Leverage:**
    *   **Equity:** 4,467 million EUR.
    *   **Financial Liabilities (Noncurrent + Current):** 5,867 + 1,022 = 6,889 million EUR.
    *   **Total Adjusted Capital (Equity + Net Financial Debt approximately):** Total assets are 21,367 million EUR, with equity at 4,467 million EUR. The company has significant financial debt (6.889 billion EUR). The ratio of debt to equity reflects a capital-intensive utility model.
    *   **Capital Expenditure:** The firm reports substantial investment in Property, Plant, and Equipment (6.162 billion EUR) and Intangible Assets (3.515 billion EUR), indicating a utility model requiring consistent heavy capex.

2.  **Market Context and Costs:**
    *   The 2022 swap curves showed a sharp increase (10Y swap ~1.9%), significantly higher than 2020-2021 levels. Hybrid debt carries a risk premium over senior debt. With current market conditions showing volatility, the cost of issuing new hybrid instruments is notably higher than in previous years.

3.  **Rationale for Hybrid Issuance:**
    *   The company has a strong EBITDA (1.505 billion EUR) but faces increasing interest costs (finance costs rose from 89 million EUR to 125 million EUR).
    *   While the company is a stable utility, the rise in interest rates and the ongoing need for transition-related capex suggest that while there is no immediate "distress," there is a clear rationale for "mild leverage optimization." 
    *   The issuance of hybrids at 7.5% would provide meaningful rating headroom without reaching the "significant leverage pressure" or "transformational M&A" levels associated with the 11.25% or 15% thresholds. It balances the need for financial flexibility against the increased cost of debt in the current interest rate environment.

4.  **Conclusion:**
    *   A2A shows moderate investment needs typical of a multi-utility. 7.5% is appropriate as it provides rating flexibility and leverage improvement during a cycle of rising interest rates, without incurring the excessive cost burdens of higher proportions, which would be unnecessary given the current EBITDA stability.

<answer>7.5%</answer>