To determine the extent to which Naturgy Energy Group SA should rely on hybrid bonds in its capital structure as of the end of 2022, we must analyze both the macroeconomic environment (specifically the pricing of credit risk) and the company's internal financial health.

1. **Macroeconomic Environment and Cost of Debt:**
Looking at the market data, interest rates and credit spreads rose sharply in 2022. The 5-year swap curve jumped from negative territory (-0.264% in 2021) to 1.726%. More importantly, the Sub-Senior Delta for the iBoxx EUR Non-Financial IG index—which measures the yield premium (spread) a company must pay to issue subordinated/hybrid debt over standard senior bonds—widened massively from 1.298% in 2021 to 2.295% in 2022. This 100-bps increase makes hybrid bonds a much more expensive source of capital relative to regular senior debt.

2. **Company's Financial Health:**
Hybrid bonds typically grant "equity credit" from rating agencies (usually 50%), which helps protect a company's credit rating without diluting shareholders. We must look at Naturgy's debt metrics to see if they need this protection:
* **EBITDA:** €4.954 billion
* **Interest Expense (Finance Costs):** €837 million
* **Total Financial Liabilities:** €13.999 billion (non-current) + €2.302 billion (current) = €16.301 billion 

This gives Naturgy an **Interest Coverage Ratio (EBITDA / Interest)** of approximately **5.9x** and a **Total Debt / EBITDA** leverage ratio of **3.3x**. For a capital-intensive utility company, a leverage ratio around 3.3x and coverage near 6x demonstrate a highly robust balance sheet, comfortably supporting a solid investment-grade rating. 

**Conclusion:**
Because the premium paid for subordinated hybrid debt became extremely expensive in 2022, and because Naturgy boasts strong coverage and leverage metrics that do not require expensive equity-like credit to defend its current rating, it is economically optimal for the company to issue standard senior debt rather than hybrid bonds. 

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