To determine the appropriate extent to which Acciona SA should issue hybrid bonds, we must analyze its current capital structure, financial performance, cash flow needs, and the cost of capital environment, applying the S&P Global Ratings methodology for Regulated Utilities and Unregulated Power/Gas (as Acciona operates in renewable energy and infrastructure).

**1. Current Capital Structure and Hybrid Status**
First, we identify the existing hybrid debt. The line item "Participaciones Preferentes Obligaciones YOtros Valores Negociables" (Preferred Shares, Bonds, and Other Negotiable Securities) is typically where hybrid instruments are recorded in Spanish GAAP/IFRS reporting for utilities.
*   **Noncurrent:** 3,101 million EUR (2023-01-01)
*   **Current:** 1,139 million EUR (2023-01-01)
*   **Total Outstanding Hybrids/Preferreds:** ~4,240 million EUR.

Next, we calculate the **Total Adjusted Capital**. S&P generally defines Adjusted Capital as Equity + Adjusted Debt. For hybrid analysis, we look at the proportion of hybrids within this base.
*   **Total Equity (2023-01-01):** 6,304 million EUR.
*   **Total Debt (Interest-bearing):**
    *   Noncurrent Loans: 2,624 million EUR
    *   Noncurrent Lease Liabilities: 439 million EUR
    *   Current Loans: 553 million EUR
    *   Current Lease Liabilities: 72 million EUR
    *   *Note: The "Participaciones Preferentes..." line is often treated as debt-like or hybrid. If we treat the 4,240m as part of the debt/hybrid bucket:*
    *   Total Interest Bearing Debt (excluding hybrids for the denominator base usually, but including for total capitalization): ~3,688 million EUR (Loans/Leases).
*   **Total Adjusted Capital Base (Equity + Debt + Hybrids):**
    *   Equity: 6,304
    *   Debt (Loans/Leases): 3,688
    *   Hybrids: 4,240
    *   **Total Capital:** ~14,232 million EUR.

*Current Hybrid Ratio:* 4,240 / 14,232 ≈ **29.8%**.
*Wait, this exceeds the 15% cap mentioned in the prompt.* The prompt asks to assess the extent to which the entity should be advised to issue hybrid bonds *between 0% and 15% of total adjusted capital*. This implies we are looking for the *target* or *incremental* advice relative to the S&P equity credit cap. However, S&P typically caps the *equity credit* granted to hybrids at 50% or 100% depending on terms, but the *volume* of hybrids relative to total capitalization is often capped at 15-20% for investment grade utilities to maintain strong credit metrics.

Let's re-read the prompt's constraint: "assess the extent to which the entity should be advised to issue hybrid bonds (between 0% and 15% of total adjusted capital)." And the options are percentages of total adjusted capital.
If the company *already* has ~30% in instruments classified as "Participaciones Preferentes...", it is possible that not all of these are rated as hybrids with equity credit by S&P, or the "Total Adjusted Capital" definition in the prompt implies a specific denominator.
However, looking at the *growth* and *needs*:

**2. Financial Performance and Cash Flow**
*   **Revenue Growth:** Increased from 8,104m to 11,195m EUR (+38%).
*   **Operating Profit (EBIT):** 1,334 million EUR.
*   **Net Income:** 615 million EUR.
*   **Operating Cash Flow (OCF):** 1,648 million EUR.
*   **Investing Cash Flow (Capex):** -1,944 million EUR (Outflow).
*   **Free Cash Flow (OCF - Capex):** 1,648 - 1,944 = **-296 million EUR**.

The company has negative free cash flow. It is investing heavily in growth (Capex nearly double the previous year's investing outflow of 1,087m).
*   **Financing Cash Flow:** +338 million EUR.
*   **Debt Issuance:** 4,021 million EUR issued vs 3,186 million EUR repaid. Net debt issuance ~835 million EUR.

The company is funding its aggressive expansion through debt issuance.

**3. Leverage and Credit Metrics**
*   **Debt/EBITDA:**
    *   EBITDA approx = Operating Profit (1,334) + Depreciation/Amortization (762) = ~2,096 million EUR.
    *   Total Debt (Loans + Leases + Hybrids?)
        *   If we include the 4,240m "Participaciones" as debt: Total Debt ~ 7,928m.
        *   Leverage = 7,928 / 2,096 ≈ **3.78x**.
    *   If we exclude Hybrids from "Debt" for standard leverage but include in Capitalization:
        *   Senior Debt ~ 3,688m.
        *   Senior Leverage = 3,688 / 2,096 ≈ **1.76x**.

A senior leverage of 1.76x is very healthy for a utility. A total leverage (including hybrids as debt) of 3.78x is moderate.
S&P Regulated Utilities with "Strong" or "Strong/Adequate" regulatory advantage can sustain higher leverage. Acciona is largely unregulated/renewable (Unregulated Power/Gas sector guidelines apply more closely to the generation side, though it has infrastructure components).
For Unregulated Power, leverage tolerance is lower. However, Acciona has long-term PPAs (Power Purchase Agreements) which de-risk cash flows.

**4. Cost of Capital and Market Environment**
*   **Swap Rates 2022:** 5Y avg 1.726%, 10Y avg 1.927%. Rates have risen significantly from 2020/2021.
*   **Corporate Bond Spreads (IG):** ~2.295% (Average).
*   **Cost of Hybrid:** Hybrids typically price at a spread of 250-350bps over the mid-swap rate or government bond.
    *   Estimated Hybrid Coupon: ~1.9% (10Y Swap) + ~3.0% (Spread for BB/Baa hybrid) ≈ **4.9% - 5.5%**.
    *   Current Cost of Debt (Finance Costs / Average Debt):
        *   Finance Costs: 256 million EUR.
        *   Average Debt (Loans): ~(2624+2073+553+280)/2 ≈ 2,765m.
        *   Implied Interest Rate on Senior Debt: 256 / 2,765 ≈ **9.2%**? This seems high. Let's look closer.
        *   Finance costs include interest on hybrids.
        *   Total Interest Bearing Liabilities (Loans + Hybrids): ~(3688 + 4240)/2 ≈ 3,964m (avg).
        *   Wait, the balance sheet shows "Participaciones Preferentes" of 3,101 (NC) + 1,139 (C) = 4,240.
        *   Total Financial Liabilities = 4,240 (Hybrids) + 3,688 (Loans/Leases) = 7,928m.
        *   Finance Costs 256m / 7,928m ≈ **3.2%**. This is a reasonable blended cost.

Issuing *new* hybrids in the current rising rate environment (2022 data) would likely come at a coupon of 5-6%, which is **higher** than the current blended cost of debt (3.2%) and likely higher than the marginal cost of senior debt if the company is IG rated (Senior spread ~2.3% + Swap 1.9% = 4.2%).
Therefore, issuing hybrids would **increase** the cost of debt.

**5. Strategic Assessment**
*   **Refinancing Needs:** The company has 1,139m in *current* "Participaciones Preferentes". This suggests a maturity or redemption window in the next 12 months. This is a **refinancing need**.
*   **Capex Needs:** High capex intensity (-1,944m investing cash flow).
*   **Leverage:** Senior leverage is low (1.76x). Total leverage is moderate.
*   **Rating Impact:** The company is likely rated BBB/A- range. Hybrids provide equity credit (usually 50% for standard hybrids). Issuing hybrids helps keep *adjusted* leverage down despite high absolute debt levels.
*   **Guideline Check:**
    *   **0%:** Incorrect. There is a refinancing need for the current portion (1.1bn) and high capex.
    *   **3.75%:** "Moderate funding needs... Cost of hybrid will increase current cost of debt." This fits. The company needs to refinance the 1.1bn current hybrid and potentially fund some capex. Issuing a small amount to refinance and slightly optimize is prudent.
    *   **7.5%:** "Meaningfully improves adjusted leverage." Given senior leverage is already low, the *urgency* to improve adjusted leverage via expensive hybrid equity is lower. The main driver is refinancing.
    *   **11.25% / 15%:** "High capex intensity... Material downgrade risk." Acciona's senior leverage is not stressed enough to warrant *maximum* hybrid issuance, especially given the high cost of hybrids in 2022. The prompt limits issuance to 3bn/year.

**Calculation of Recommendation:**
The company has ~1.14bn in current hybrids maturing/refinancing.
Total Adjusted Capital (Equity 6,304 + Debt 3,688 + Hybrids 4,240) = ~14,232m.
1.14bn refinancing is ~8% of Total Capital.
However, the question asks for the *extent* to which they should be *advised to issue*.
If they simply refinance the 1.14bn, the outstanding amount remains similar.
Does it need *new* net issuance?
FCF is negative (-296m). It issued net 835m in debt.
The balance sheet grew significantly (Assets +3bn).
The "Participaciones Preferentes" increased from 2,364 (NC) + 1,666 (C) = 4,030m in 2022 to 4,240m in 2023. Net increase of ~210m.
The company is *already* using hybrids.

The key constraint is the **cost**. In 2022, hybrid costs rose sharply. S&P guidelines state:
*   If cost of hybrid materially increases cost of debt -> Lean towards 0% or 3.75%.
*   If rating headroom is constrained -> Lean higher.

Acciona's senior leverage (1.76x) is very comfortable. It does not *need* hybrid equity credit to preserve an IG rating on senior debt. It needs hybrids primarily for **refinancing** the existing stock and perhaps minor optimization.
The "Current" portion of 1,139m must be addressed.
If we advise issuing **3.75%** of Total Adjusted Capital (~14,232m * 0.0375 = **533 million EUR**), this covers a significant part of the refinancing need without aggressively expanding the expensive hybrid book.
If we advise **7.5%** (~1,067 million EUR), this covers the entire current maturity refinancing.
Given the "High Capex" and negative FCF, maintaining the hybrid buffer is important. However, the *cost* argument is strong against aggressive new issuance.
The prompt options are discrete.
0% is too low (ignores refinancing).
15% is too high (costly, not needed for leverage).
Between 3.75% and 7.5%:
The company has a "Moderate refinancing" need (1.1bn current).
7.5% of 14.2bn is ~1.07bn. This aligns perfectly with refinancing the current tranche.
3.75% is ~530m. This would only cover half.

However, look at the **Total Adjusted Capital** definition again. If S&P grants only 50% equity credit, the "Adjusted Capital" for leverage ratios might be different. But the prompt asks for % of *Total Adjusted Capital* (Equity + Adjusted Debt).
Let's look at the "Cap" logic. The cap is 15%.
Current Hybrid % = 4,240 / 14,232 = 29.8%.
This implies the company is *already* above the 15% "advisory" band if we count all "Participaciones" as hybrids.
*Correction:* In many utility structures, "Participaciones Preferentes" might include instruments that are not rated as hybrids by S&P, or the "Equity" figure already includes some hybrid equity credits.
Alternatively, the "15% cap" refers to the *incremental* or the *target* for *new* advice relative to a baseline.
But usually, these questions imply: "What % of Total Capital should be in Hybrids?"
If the company is *already* at ~30%, advising *more* issuance to reach 15% makes no sense (it's already above).
This suggests that perhaps the "Participaciones Preferentes" are **not** all considered hybrids for the purpose of this specific S&P metric, or the "Total Adjusted Capital" denominator is much larger (e.g., including deferred taxes, provisions, etc., though S&P usually strips those).
Or, more likely, the question implies: **What is the optimal *additional* issuance or the *target level*?**
If the current level is effectively "high" (30%), and costs are rising, the advice should be to **limit** new issuance to essential refinancing.

Let's re-evaluate the "0%" criteria: "No current hybrid in the capital structure." Acciona *has* hybrids. So 0% is incorrect.
"3.75%": "Moderate funding needs... Cost of hybrid will increase current cost of debt."
"7.5%": "Moderate refinancing... Meaningfully improves adjusted leverage."

Given the high existing stock, the marginal benefit of *new* hybrids is low, and the cost is high. The primary need is refinancing the 1.14bn current portion.
If the company issues 7.5% of Total Capital (~1.1bn), it refinances the current portion. This maintains the status quo.
If it issues 3.75% (~0.5bn), it reduces the hybrid book, deleveraging the "expensive" capital, which might be wise if senior debt is cheaper.
However, utilities typically maintain a hybrid buffer for rating flexibility.
The "High Capex" (-1.9bn) suggests a need for flexible capital. Hybrids are flexible (deferrable coupons).
Despite the cost, the **rating preservation** and **capex funding** argument leans towards maintaining the hybrid buffer.
The most standard "Moderate" advice for a utility with refinancing needs and high capex, where cost is a concern but not prohibitive, is **7.5%**. It covers the refinancing need (1.1bn is approx 7.5% of 14.2bn) and stabilizes the capital structure.

Let's check the math on 7.5%:
Total Adjusted Capital ≈ 14,232m.
7.5% = 1,067m.
Current Maturity = 1,139m.
This is a near-perfect match for a "Refinancing" scenario.

Therefore, the advice is to issue hybrids to cover the refinancing need, which corresponds to approximately 7.5% of total adjusted capital.

<answer>7.5%</answer>