I need to analyze Acciona SA's capital structure and determine how much they should utilize hybrid bonds relative to S&P Global Ratings' 15% cap on equity credit from hybrids.

First, let me identify the relevant financial data from the annual report:

**Equity (2023-01-01):** 6,304,000,000 EUR
**Equity (2022-01-01):** 5,557,000,000 EUR

**Debt components (2023-01-01):**
- Participaciones Preferentes Obligaciones YOtros Valores Negociables No Corrientes1 (Non-current financial instruments): 3,101,000,000 EUR
- Noncurrent Portion Of Noncurrent Loans Received: 2,624,000,000 EUR
- Noncurrent Lease Liabilities: 439,000,000 EUR
- Participaciones Preferentes Obligaciones YOtros Valores Negociables Corrientes (Current financial instruments): 1,139,000,000 EUR
- Current Loans Received And Current Portion Of Noncurrent Loans Received: 553,000,000 EUR
- Current Lease Liabilities: 72,000,000 EUR

**Total Debt (2023-01-01):**
= 3,101 + 2,624 + 439 + 1,139 + 553 + 72 
= 7,928,000,000 EUR

**Total Adjusted Capital** = Debt + Equity = 7,928 + 6,304 = 14,232,000,000 EUR

**S&P Cap on hybrid equity credit:** 15% of total adjusted capital
= 15% × 14,232,000,000 = 2,134,800,000 EUR

Now, looking at Acciona's existing hybrid-like instruments:
- The "Participaciones Preferentes Obligaciones YOtros Valores Negociables" (preferred shares, bonds and other negotiable securities) total 3,101 + 1,139 = 4,240,000,000 EUR

These appear to include hybrid bonds. However, I need to assess how much equity credit S&P would give.

Looking at the company's capital structure and the nature of these instruments, the non-current portion of 3,101,000,000 EUR likely includes longer-term hybrid bonds that could qualify for equity credit.

**Key considerations for hybrid bond utilization:**

1. **Current leverage position:** Debt/Equity = 7,928/6,304 = 1.26x or Debt/(Debt+Equity) = 7,928/14,232 = 55.7%

2. **Existing hybrid-like instruments:** The company already has significant preferred securities and bonds outstanding (4,240,000,000 EUR total).

3. **S&P's 15% cap:** Maximum equity credit from hybrids = 2,134,800,000 EUR

4. **Market conditions in 2022:** Interest rates rose significantly (5Y swap at 1.726%, 7Y at 1.806%, 10Y at 1.927%), making hybrid bonds more expensive than in previous years.

5. **Company's credit profile:** With a BBB/BBB- type rating likely (given the hybrid focus), Acciona needs to balance:
   - Tax efficiency of debt (interest deductible)
   - Equity credit benefits (improving leverage metrics)
   - Cost of hybrids vs. regular debt

6. **Current utilization assessment:**
   - If we assume the 3,101,000,000 EUR non-current preferred/bonds include hybrids that get 50-100% equity credit, and perhaps 1,500,000,000-2,000,000,000 EUR are true hybrids...
   - The company appears to already be using hybrids substantially.

Given:
- The company already has significant preferred securities outstanding
- The 15% cap limits equity credit to ~2.1 billion EUR
- In 2022, rising interest rates made hybrids more expensive
- The company has good equity base (6.3 billion EUR)
- They need to maintain financial flexibility

The optimal strategy would be to utilize hybrids up to a meaningful portion of the cap but not maximize it, leaving headroom for future needs and rating stability.

Looking at the options: 0%, 25%, 50%, 75%, or 100% of the cap.

- 0%: Too conservative, misses equity credit benefits
- 25% (~534M EUR): Modest, likely underutilizing
- 50% (~1,067M EUR): Balanced approach, good equity credit without over-reliance
- 75% (~1,601M EUR): Aggressive, significant equity credit but less headroom
- 100%: Maximum, no headroom, potentially risky if S&P changes view

Given Acciona's infrastructure/renewable energy profile (capital intensive, stable cash flows), hybrids are suitable. However, with rising rates in 2022 and the need to preserve financial flexibility, **50%** utilization represents a prudent balance—capturing meaningful equity credit benefits while maintaining headroom for growth capex (which was very high at 2,195M EUR in 2022) and potential M&A.

The company already shows significant non-current financial instruments, suggesting they're already using some hybrid capacity. A 50% target allows optimization without maxing out the cap.

<answer>50%</answer>