To determine the appropriate reliance on hybrid bonds in the capital structure for Iberdrola S.A., we must consider its financial position at the end of 2022 and the market environment.

1.  **Financial Profile:** Iberdrola is a capital-intensive utility company with substantial long-term assets (131.3 billion EUR in non-current assets) and significant financial liabilities (44.2 billion EUR in non-current financial liabilities). The company is heavily involved in long-term infrastructure projects (Construction In Progress: 11.5 billion EUR).
2.  **Cost of Debt and Market Trends:** The market data shows a significant increase in interest rates from 2021 to 2022 across all swap curves (5Y, 7Y, 10Y). For example, the 10Y Swap average rose from 0.053% in 2021 to 1.927% in 2022. Rising interest rates make traditional debt more expensive to service and refinance.
3.  **Role of Hybrids:** Hybrid bonds are often used by utilities to optimize capital structure, as they offer equity-like characteristics (often treated as partial equity by rating agencies) while providing interest deductibility. This helps maintain credit ratings while funding high levels of capital expenditure.
4.  **Capital Structure Management:** Iberdrola maintains a robust equity base (58.1 billion EUR). However, the increase in financial liabilities and the volatile interest rate environment suggest a balanced approach. Relying exclusively (100%) or mostly (75%) on hybrids would be risky due to their higher coupon rates and complexity compared to senior debt. Conversely, 0% ignores the capital efficiency benefits. A 25% allocation represents a prudent, supplementary use of hybrid instruments to manage leverage without over-reliance on more expensive, non-traditional debt, aligning with the conservative nature of the utility sector.

<answer>25%</answer>