To determine the extent to which Hera S.p.A. should utilize hybrid bonds relative to S&P Global Ratings' cap, we must first calculate the maximum amount of hybrid bonds allowed under the cap and then assess the optimal amount for the company to issue.

**1. S&P Global Ratings' Cap Calculation:**
S&P limits the equity credit on hybrids to a maximum of 15% of total adjusted capital (defined as Debt + Equity). 
From the 2022 annual report data:
- Total Equity = €3,644,700,000
- Total Liabilities (Debt) = €13,473,800,000
- Total Adjusted Capital = Debt + Equity = €17,118,500,000

Maximum hybrid bonds allowed for full equity credit = 15% × €17,118,500,000 = €2,567,775,000.

**2. Optimal Utilization Analysis:**
- **Interest Rate Environment:** The provided market data shows a rapidly rising interest rate environment in 2022. The 5Y, 7Y, and 10Y swap curves have shifted from negative averages in 2020-2021 to strongly positive averages in 2022 (1.72% - 1.92%). Corporate bond yields (iBoxx EUR Non-Financial IG) have also risen significantly, averaging around 2.3% in 2022. Issuing long-term hybrid bonds in this kind of bearish, rising-rate environment locks in high coupon costs.
- **Current Capital Structure & Needs:** Hera's current financial liabilities (both current and non-current) total approximately €6.34 billion, and the company shows a healthy equity base. There is no immediate distress or massive funding gap that would necessitate maximizing hybrid issuance at unfavorable rates.
- **Credit Agency Flexibility:** If a company issues hybrids beyond the 15% cap, the excess amount receives 0% equity credit from S&P, meaning it is treated entirely as debt, worsening the Debt/Equity ratio without the benefit of equity credit. 
- **Strategic Sizing:** Because of the high interest rates, Hera should only issue hybrids to the extent necessary to efficiently manage its weighted average cost of capital (WACC) and maintain its target credit rating without overpaying for equity credit. This points to a moderate, partial utilization of the cap rather than maximizing it (100%) or completely avoiding it (0%). A 50% utilization represents a balanced approach, taking advantage of the equity credit buffer to support the balance sheet without over-leveraging into expensive, subordinated debt during a rate hiking cycle.

<answer>50%</answer>