I'll analyze Acciona SA's financial position and capital structure to determine an appropriate level of hybrid bond reliance.

## Key Financial Metrics Analysis

**Leverage and Capital Structure:**
- Total Equity (2023): €6,304M
- Total Debt (non-current financial liabilities excluding leases): ~€5,725M (bonds €3,101M + loans €2,624M)
- Current financial debt: ~€1,692M (bonds €1,139M + loans €553M)
- Total financial debt (ex-leases): ~€7,417M
- Net debt: ~€7,417M - €2,360M cash = ~€5,057M
- Debt-to-equity ratio: ~1.18x
- Net debt/EBITDA: EBITDA ≈ Operating profit (€1,334M) + D&A (€762M) + Impairments (€15M) ≈ €2,111M → Net debt/EBITDA ≈ 2.4x

**Profitability:**
- Revenue grew 38% YoY (€8,104M → €11,195M)
- Operating profit margin: ~12%
- Net income: €615M (up from €404M)
- Interest coverage: EBITDA/Finance costs = €2,111M/€256M ≈ 8.2x

**Cash Flow:**
- Operating cash flow: €1,648M (strong improvement from €574M)
- Heavy capex: €2,195M in PPE/intangibles
- Free cash flow is negative, indicating significant growth investment

## Hybrid Bond Considerations

**Factors favoring hybrid bonds:**
1. Acciona is a capital-intensive infrastructure/energy company with significant investment needs (capex €2.2B)
2. Moderate leverage (2.4x net debt/EBITDA) leaves room for optimization
3. The company already uses a mix of bonds and bank loans
4. Hybrid bonds could provide equity credit from rating agencies, improving leverage metrics
5. Strong and growing EBITDA supports coupon payments
6. Interest rate environment has risen significantly (swap curves moved from negative to ~1.7-1.9%), making pure debt more expensive

**Factors limiting hybrid use:**
1. The company already has solid equity (€6.3B) and reasonable leverage
2. Interest coverage is healthy at 8.2x
3. Hybrid bonds are more expensive than senior debt
4. The company has non-controlling interests of €1.4B providing additional equity-like cushion
5. Heavy capex needs suggest they need flexibility - too much hybrid could be costly
6. Sub-senior spreads are elevated (2.3% average in 2022 with 0.2 delta above IG corporates)

**Appropriate level:**
Acciona is a large infrastructure/renewables company with investment-grade characteristics. Such companies commonly use hybrid bonds as a modest portion of their capital structure - typically to optimize their credit ratings and maintain investment-grade status while funding growth. The company's moderate leverage and strong cash flows suggest it doesn't need heavy reliance on hybrids. A 25% allocation to hybrid bonds within their capital structure would be appropriate - enough to benefit from equity credit treatment and optimize the capital structure, but not so much as to incur excessive costs. This is consistent with how comparable European infrastructure/utility companies typically use hybrids as a complementary tool.

<answer>25%</answer>