I'll analyze Iberdrola's capital structure and financial position to determine the appropriate reliance on hybrid bonds.

**Key Financial Metrics from 2022:**

1. **Equity Structure:**
- Total Equity: €58.114 billion (2023-01-01)
- Equity attributable to owners: €41.119 billion
- Noncontrolling interests: €16.995 billion
- Issued capital: €4.772 billion

2. **Debt Structure:**
- Noncurrent financial liabilities: €44.216 billion
- Current financial liabilities: €25.079 billion
- Total financial debt: ~€69.3 billion

3. **Hybrid/Equity-like Instruments Already Present:**
- "Instrumentos De Capital Con Caracteristicas De Pasivo Financiero No Corriente" (Noncurrent capital instruments with financial liability characteristics): €576 million
- "Instrumentos De Capital Con Caracteristicas De Pasivo Financiero Corriente" (Current): €87 million
- Total hybrid capital instruments: ~€663 million

4. **Perpetual Subordinated Bonds (Obligaciones Perpetuas Subordinadas):**
- Emission in 2021-2022: €2.74 billion
- Interest accrual on these: €169 million in 2022-2023

5. **Key Ratios:**
- Debt/Equity ratio: ~69.3/58.1 = 1.19x or debt-to-total capital ~54%
- The company has significant debt but also substantial equity base

**Analysis of Capital Structure Needs:**

1. **Credit Rating Considerations:**
- Iberdrola is a large regulated utility with stable cash flows
- Utilities typically benefit from hybrid bonds due to:
  - Stable, predictable cash flows
  - High capital intensity requiring long-term financing
  - Regulatory asset bases providing earnings stability

2. **Current Hybrid Usage:**
- The company already uses some hybrid instruments (perpetual subordinated bonds ~€2.74 billion, other capital instruments ~€0.66 billion)
- Total hybrid-like instruments: ~€3.4 billion vs total capital of ~€127 billion = ~2.7% currently

3. **Market Environment (2022):**
- Interest rates rose significantly (swap curves turned positive in 2022 after negative rates)
- Corporate bond spreads widened (iBoxx non-financial IG at 2.295% average in 2022)
- Higher rate environment makes fixed-rate hybrids more attractive for issuers

4. **Regulatory/Utility Sector Characteristics:**
- Utilities have high tangible assets (PP&E: €86.3 billion) - good collateral for debt
- Stable EBITDA (€13.2 billion in 2022) supports interest payments
- Long asset lives match well with perpetual/perpetual-like instruments

5. **Optimal Capital Structure for Utilities:**
- Utilities typically target BBB+/A- type ratings
- Hybrid bonds help: 
  - Diversify funding sources
  - Lower cost of capital (equity credit from rating agencies)
  - Match long-duration assets with long-duration liabilities
  - Provide buffer equity credit (typically 50-100% equity treatment from rating agencies)

6. **Financial Flexibility Assessment:**
- Strong operating cash flows: €10.4 billion
- Heavy capex needs: €6.3 billion property plant & equipment + €0.5 billion intangibles
- Net investing outflows: €10.2 billion
- The company is capital intensive with ongoing investment needs

**Determining Optimal Hybrid Share:**

Given:
- Current hybrid usage is very low (~2.7% of total capital)
- Utility sector benefits significantly from hybrid treatment (rating agencies give 50% equity credit)
- Stable cash flows support hybrid coupon payments
- Need to balance: cost savings vs. financial flexibility vs. rating agency treatment

Rating agencies typically give:
- 50% equity credit for hybrid bonds up to certain thresholds (usually 10-15% of total capitalization)
- 100% equity treatment for some deeply subordinated perpetual instruments

For a utility like Iberdrola:
- Too low (0%): Missing cost savings and diversification benefits
- 25%: Reasonable - provides meaningful equity credit and cost savings without over-reliance
- 50%: High for a utility - might constrain financial flexibility
- 75-100%: Excessive - too much reliance on hybrids risks rating downgrade if market turns

The 25% level provides:
- Meaningful diversification of funding sources
- Rating agency equity credit benefits (improving leverage metrics)
- Cost savings vs. pure equity
- Maintains financial flexibility for growth capex
- Matches long-duration assets with long-duration capital

Higher levels (50%+) would risk:
- Reduced financial flexibility in stress scenarios
- Potential rating agency changes to equity credit
- Refinancing risk for large hybrid maturities

<answer>25%</answer>