Let’s break this down step by step.

**1. What we know about the company from the data**  
- The company is Naturgy Energy Group, S.A., a Spanish utility.  
- As of 2023-01-01, total assets are €40,390 million and equity is €9,979 million.  
- Financial liabilities (noncurrent + current borrowings and leases) are considerable — long-term borrowings alone are €12,689 million.  
- There’s a clear trend of profitability, with net income attributable to the parent of €1,649 million in 2022.  
- Operating cash flows are strong (€4,242 million in 2022), comfortably covering investment and financing needs.

**2. Market context (2020–2022)**  
- Swap rates were negative or low in 2020–2021 before rising significantly in 2022, increasing refinancing costs.  
- Corporate bond yields (iShares Core Euro Corp Bond) and subordinated spreads also rose in 2022. Issuing hybrids became more expensive relative to the prior low-rate environment.  
- Despite higher rates, Naturgy’s credit profile (utility, stable cash flows) makes it a plausible candidate for hybrid issuance.

**3. S&P cap and rationale for use**  
- S&P caps equity credit from hybrids at 15% of total adjusted capital (debt + equity).  
- For a company like Naturgy, hybrids can be used to support the rating while maintaining financial flexibility, especially given heavy infrastructure investments.  
- However, the relatively high interest rate environment in 2022 meant the cost of hybrid capital was higher, and Naturgy’s leverage was not extremely aggressive — equity is ~25% of total assets, suggesting moderate usage.  
- The question is about how much of the allowed 15% cap they should *utilize*. Given sound cash flow, reasonable leverage, and costly issuance conditions, a moderate but not full utilization seems appropriate — around 50% of the cap would give a rating buffer without overpaying for equity credit.

**4. Conclusion**  
They would likely target a middle ground — using hybrids for some equity credit but not pushing to the maximum allowed, aligning with both financial strategy and market pragmatism.

<answer>50%</answer>