Reasoning:

Naturgy has a highly capital-intensive infrastructure/utility asset base and significant leverage, which are typical conditions where hybrid bonds can be useful because rating agencies may grant partial equity credit while the instrument remains cheaper than common equity.

Key considerations:

- Leverage is material. At year-end 2022, financial liabilities were about €16.3bn, including non-current financial liabilities of €14.0bn and current financial liabilities of €2.3bn. Equity was €10.0bn. This means debt is substantial relative to equity and total capital.
- Operating cash generation improved strongly in 2022. Cash flow from operating activities rose to €4.24bn from €1.00bn in 2021, and EBITDA increased to €4.95bn from €3.53bn. This supports capacity to service hybrid coupons.
- The company pays significant dividends. Dividends/distributions were material, with €1.5bn cash paid in financing activities and dividends per share of €1.20 recognized plus €0.50 proposed/declared. Hybrids can help protect credit metrics while maintaining shareholder distributions, but excessive use would add fixed financial burden.
- Market rates rose sharply in 2022. Swap rates moved from near zero/negative in 2021 to around 1.7%–1.9% in 2022, and credit spreads also widened. This makes hybrid issuance more expensive than in prior years, arguing against using the full S&P cap.
- The company already has a relatively stable regulated/contracted business profile, but it also faces volatility from energy markets, derivatives, working capital, and high investment needs. A meaningful but not maximal hybrid buffer is appropriate.

Overall, Naturgy should make meaningful use of hybrids because they are well suited to its utility balance sheet and can support credit metrics, but the higher 2022 rate environment and already significant cash commitments argue against fully utilizing the S&P Global Ratings 15% adjusted-capital cap. A moderate-to-high utilization is most appropriate.

<answer>75%</answer>