Based on the provided financial statements and S&P rating methodology, here is the assessment for Naturgy Energy Group’s recommended hybrid bond issuance level.

### 1. Business Risk Profile Assessment
Naturgy is a diversified Spanish utility operating in regulated networks, renewable generation, and liberalized gas/electricity supply. The S&P methodology for "Regulated Utilities" and "Unregulated Power And Gas" applies.
*   **Regulatory Advantage:** Naturgy operates in Spain, which has a history of regulatory intervention (e.g., retroactive changes to renewables subsidies, clawback mechanisms), affecting stability and predictability. This points to an adequate, rather than strong, regulatory framework.
*   **Unregulated Activities:** The company engages in gas supply and renewable generation. While renewables benefit from some long-term contracts (PPAs), Naturgy is also exposed to merchant risk in liberalized markets. Competitive advantage here is likely satisfactory or adequate.
*   **Scale, Scope, and Diversity:** The company is large in scale (€40bn assets, €34bn revenue), operates across the gas and electricity value chain, and is geographically diverse (mainly Spain, with operations in Latin America). This supports a **strong/adequate** assessment.

### 2. Financial Risk Profile Assessment
*   **Capital Structure:** The company has existing hybrid bonds, first issued in 2013. As of Dec 31, 2022, the capital structure includes a moderate amount of hybrid debt (implied by "Noncurrent Financial Liabilities" and the note stating they issued hybrids).
*   **Leverage:** The provided S&P Net Debt / EBITDA ratio for 2022 is **2.67x**. This is a moderate level for a utility.
*   **Cash Flow Leverage:** The S&P FFO / Net Debt for 2022 is **0.2847 (28.47%)**. This aligns with a solid "BBB" to "A" range credit profile for the sector, dependent on volatility table application.
*   **Financial Policy:** Dividends are substantial (€1.2/share, totaling approx. €1.5bn per the cash flow statement), and share buybacks are present (€503m in 2022). This signals a shareholder-friendly financial policy, which often leads to a higher need for equity credit to offset aggressive distributions.

### 3. Guidance Checklist Analysis
*   **Previous Levels of Hybrid Bond Issuance:** The entity was an early adopter of hybrid bonds (2013) and has continuously maintained them in its capital structure. This is a *strong* indicator that the management and board are open to using hybrids as a permanent part of their capital structure to manage credit metrics. The Moody’s observation of "improving" adjusted leverage trend suggests the current hybrid level is effectively supporting the profile.
*   **Funding Needs:** The company has significant ongoing capital spending (€1.75bn in investing activities in 2022, excluding M&A). The refinancing needs are moderate-to-high given the existing debt stack (€13bn in long-term borrowings).
*   **Leverage Optimization:** With an FFO/Debt near 28.5% and Net Debt/EBITDA at 2.67x, Naturgy likely sits in the "BBB+" or "A-" rating category. To maintain this strong investment-grade profile amid generous shareholder distributions and high capex, hybrid issuance is an effective tool to manage adjusted leverage metrics.
*   **Cost of Hybrid:** In 2022, the 5Y swap rate averaged 1.726%, and the iBoxx corporate bond yield averaged 1.085%. A subordinated hybrid bond yield in the ~2.3% area is a marginal cost for a company generating an EBITDA margin of ~14.6% (€4.95bn EBITDA / €33.97bn Revenue). The cost would have a marginal impact on the current cost of debt.

### 4. Determining the Recommended Level
Given the "BBB+/A-" rating profile and the need to offset aggressive shareholder returns, a moderate level of hybrid capital is appropriate.
*   **0%** and **3.75%** are too low. The company already uses hybrids actively, and reducing to zero or near-zero would unmask leverage, potentially pressuring the rating.
*   **15%** is the S&P cap and is typically reserved for entities with material downgrade risk or very high M&A/capex needs.
*   **11.25%** represents a high "core" utility portfolio usage, aligning with an issuer that has significant capital intensity and a clear policy of using hybrids. It provides a buffer for the aggressive financial policy.
*   **7.5%** is appropriate for moderate refinancing/acquisition needs where hybrid issuance meaningfully improves adjusted metrics.

Considering Naturgy maintains a strong operational profile but faces regulatory risk and has a very shareholder-friendly distribution policy (including buybacks), the need for rating headroom is material. The historically established use of hybrids supports a meaningful, but not maximum, target allocation. An **11.25%** allocation effectively supports the adjusted leverage trajectory and preserves rating flexibility against unforeseen regulatory or market volatility, without pushing to the absolute 15% limit which might signal distress or transformational M&A (which is not present). It signals a proactive, rather than reactive, capital management stance.

<answer>11.25%</answer>