I need to analyze whether IBERDROLA SA should utilize hybrid bonds up to S&P Global Ratings' 15% cap of total adjusted capital.

First, let me understand what hybrid bonds are and why companies use them:
- Hybrid bonds are debt instruments with equity-like features (perpetual or very long maturity, deferrable coupons, subordination)
- They receive partial equity credit from rating agencies (typically 50-100% equity credit depending on structure)
- S&P limits this equity credit to 15% of total adjusted capital (debt + equity)

Let me examine IBERDROLA's capital structure and financial characteristics from the data:

**Capital Structure (2023-01-01 / end of 2022):**
- Equity: €58,114 million
- Equity Attributable to Owners: €41,119 million
- Noncontrolling Interests: €16,995 million

**Debt/Liabilities:**
- Noncurrent Financial Liabilities: €44,216 million
- Current Financial Liabilities: €25,079 million
- Total Financial Liabilities: €69,295 million

**Key debt components:**
- "Deudas Con Entidades De Credito Y Obligaciones U Otros Valores Negociables" (noncurrent): €36,129 million
- "Deudas Con Entidades De Credito Y Obligaciones U Otros Valores Negociables Corrientes" (current): €10,458 million
- Total bank debt/bonds: ~€46,587 million

**Total Adjusted Capital = Debt + Equity:**
Using total financial liabilities: €69,295 + €58,114 = €127,409 million

15% cap on hybrid equity credit: 0.15 × €127,409 = €19,111 million

**Key observations about IBERDROLA:**

1. **Already has hybrid-like instruments**: The data shows "Instrumentos De Capital Con Caracteristicas De Pasivo Financiero" (capital instruments with financial liability characteristics):
   - Noncurrent: €576 million
   - Current: €87 million
   - Total: €663 million

These appear to be existing hybrid/perpetual instruments. The data also shows "Obligaciones Perpetuas Subordinadas" (subordinated perpetual obligations) activity in equity movements.

2. **Strong credit metrics needed for hybrid issuance**: 
   - The company has significant debt (€69.3 billion financial liabilities)
   - EBITDA: €13,228 million
   - Debt/EBITDA ratio: roughly 5.2x (using financial liabilities/EBITDA)

3. **Business characteristics favoring hybrids**:
   - Regulated utility with stable, predictable cash flows
   - Capital intensive (PP&E of €86.3 billion)
   - Long-term infrastructure assets
   - Strong revenue growth (€53.9 billion vs €39.1 billion prior year)

4. **Market conditions in 2022**:
   - Rising interest rate environment (swap curves turned positive in 2022 after negative rates)
   - Corporate bond spreads widened (iBoxx non-financial IG at 2.295%)
   - This makes fixed-rate hybrid issuance more expensive than during 2020-2021

5. **Existing hybrid utilization**: The company already has some hybrid instruments but at relatively small levels compared to the 15% cap.

**Analysis of optimal utilization:**

- **0%**: Would ignore a valuable financing tool for a capital-intensive utility. Not optimal.
- **25%**: Conservative approach, using only a small portion of available capacity.
- **50%**: Moderate approach, using meaningful hybrid capacity while preserving flexibility.
- **75%**: Aggressive approach, using most available capacity.
- **100%**: Maximum utilization at the 15% cap.

**Key considerations for IBERDROLA:**

1. **Regulated utility profile**: Stable cash flows support higher hybrid usage as regulators often treat hybrid coupons as debt-like costs. However, some regulators may limit equity credit recognition.

2. **Growth capex needs**: The company has €11.5 billion in construction in progress, indicating significant capital needs. Hybrids can fund growth without diluting equity holders.

3. **Credit rating optimization**: As a BBB+/A- type utility (typical for Iberdrola), using the full 15% hybrid capacity helps optimize the debt/equity mix and protect ratings.

4. **Market timing**: 2022 was a challenging year for issuance with rising rates, but the company's existing hybrids and strong market position would allow execution.

5. **Peer comparison**: European utilities typically use 50-100% of their hybrid capacity. Iberdrola is a sophisticated issuer with active capital management.

6. **Financial flexibility**: Using 75-100% of capacity provides maximum equity credit benefit but reduces future flexibility. However, the 15% cap is a hard limit, so using it fully makes sense if the company can issue efficiently.

Given IBERDROLA's:
- Strong, stable utility cash flows
- Significant capital expenditure requirements (energy transition, renewables)
- Sophisticated capital markets access
- Existing demonstrated use of hybrid instruments
- Need to optimize cost of capital while preserving ratings

The company should utilize a **high percentage** of the available hybrid capacity. European utilities with strong credit profiles and heavy capex programs typically target near the maximum. The 2022 rising rate environment might cause some caution, but the structural benefits of hybrids for this type of company remain compelling.

A **75%** utilization represents an aggressive but prudent approach - using most of the capacity while retaining some flexibility for market timing or regulatory changes. This balances optimization with prudence, recognizing that:
- Full 100% might constrain future flexibility
- The company already has some hybrids in place
- Market conditions in 2022 were less favorable than prior years
- Regulatory treatment of hybrids in some jurisdictions may evolve

However, given Iberdrola's strong market position, active capital management, and the strategic importance of the 15% equity credit for ratings optimization, **75%** is the most appropriate target.

<answer>75%</answer>