Let’s assess this step by step.

**1. Nature of the entity & industry**  
Naturgy Energy Group SA is a Spanish utility with significant regulated and unregulated gas and electricity activities. Given its infrastructure-heavy balance sheet, it fits under S&P’s **regulated utilities** and **unregulated power & gas** frameworks. Its revenue (€33.97bn in 2022) and asset base (~€40bn) place it as a large, diversified European utility.

**2. Financial strength and credit context**  
- 2022 EBITDA: €4,954m, up from €3,529m in 2021.  
- Operating profit: €3,083m, net income to parent: €1,649m.  
- Total equity (end of 2022): €9,979m.  
- Debt metrics: Non-current financial liabilities: €13,999m, current: €2,302m = gross debt ~€16.3bn.  
- Cash: €3,985m, so net debt ≈ €12.3bn.  
- Net debt/EBITDA ≈ 2.5x, FFO/debt likely strong.  
- Interest costs: €837m finance costs vs. €4954m EBITDA, coverage healthy.  

This suggests **solid investment-grade metrics**, likely in the “BBB+” to “A-” range before adjustments.

**3. Refinancing and capex needs**  
- Cash flow from operations: €4,242m.  
- Investing outflows: €1,769m (including €1,687m capex).  
- Dividends paid: ~€1.5bn.  
- Net debt issuance in 2022 was slightly negative.  
No evidence of extraordinary M&A or transformative capex program. Moderate organic investment.

**4. Current hybrids and adjusted capital**  
No hybrid bonds are explicitly disclosed in the data (non-current financial liabilities appear to consist of borrowings and leases). So, starting hybrid share is **0%**.  
S&P cap is 15% of total adjusted capital (Equity + Adjusted Debt). Given ~€10bn equity and ~€16bn debt, 15% would be ~€3.9bn—above the €3bn annual issuance limit, but still possible over time.

**5. Rate environment and cost of hybrid**  
2022 swap rates surged (5Y average 1.73%, 10Y 1.93%). IG EUR credit spreads widened (Sub-sen delta ~2.3% in 2022).  
A hybrid issue would price well above senior debt, meaning a **materially higher cost** than current average debt cost (implied ~2–3% based on finance costs/gross debt). This makes hybrids less attractive.

**6. Rating and leverage context**  
- Naturgy’s leverage and coverage metrics appear strong.  
- No imminent downgrade risk.  
- Hybrid issuance would moderately improve adjusted leverage but is not needed for rating stability.  
- Given solid cash flow generation, refinancing needs are moderate and manageable.

**7. Guideline mapping**  
- No current hybrids.  
- No extraordinary capex/M&A.  
- Strong cash generation and comfortable leverage.  
- Cost of hybrid meaningfully above current debt cost.  
- Hybrid would provide limited rating flexibility, not a necessity.  

This points strongly to **0%** or possibly **3.75%** for mild leverage optimization, but the high cost and lack of urgent need argue against even that.

**Conclusion**: 0% is most appropriate in the next 18 months.

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