Hybrid bonds are perpetual or deeply subordinated instruments that combine debt and equity features, and are often treated partly as equity by rating agencies. Evaluating the appropriate reliance on hybrid bonds for Iberdrola requires analyzing its capital structure, financial performance, cash flows, and the market environment.

From the balance sheet data:
- Total assets: €154.7 billion
- Total equity: €58.1 billion (including non-controlling interests of €17.0 billion)
- Non-current financial liabilities: €44.2 billion
- Current financial liabilities: €25.1 billion
- Total financial debt is substantial, roughly €69.3 billion plus lease liabilities (~€2.4 billion)

The income statement shows:
- EBITDA: €13.2 billion
- Interest costs: €3.0 billion (up from €2.3 billion the prior year)
- Finance income/cost net: -€1.8 billion
- Profit attributable to parent: €4.3 billion

Cash flow statement:
- Operating cash flow: €10.4 billion
- Investing cash flow: -€10.2 billion (heavy capex, especially in PP&E at €6.3 billion)
- Financing cash flow: €0.15 billion

The company already uses perpetual subordinated instruments (obligaciones perpetuas subordinadas), with interest accrued of €169 million in 2022, indicating existing hybrid debt. Changes in non-controlling interests and perpetual issuances in prior years (€2.74 billion in 2021) show active hybrid usage.

Market data shows sharply rising interest rates in 2022 (5Y swap from -0.26% to +1.73%). The cost of hybrids would increase significantly. The iShares Core Euro Corp Bond yield also rose, and subordinated spreads widened, making hybrids more expensive relative to senior debt. Given the rate environment and Iberdrola’s already significant leverage, a moderate reliance on hybrids (like 25%) would balance the benefits of equity credit from rating agencies with the higher coupon costs, while not over-relying on expensive subordinated financing.

Iberdrola’s stable regulated and contracted cash flows support some hybrid usage, but heavy capex needs and rising rates suggest a conservative approach. A 25% reliance allows partial equity credit without excessive interest burden.

<answer>25%</answer>