To determine the extent to which ENGIE should be advised to issue hybrid bonds, we analyze the company's financial position, capitalization metrics, and S&P Global Ratings' guidelines for total adjusted capital (TAC).

**1. Current Hybrid Bond Allocation & Total Adjusted Capital (TAC):**
S&P calculates TAC as the sum of Adjusted Equity and Adjusted Debt.
*   **Reported Equity:** €39.28 billion (which includes €3.39 billion in Deeply Subordinated Perpetual Notes, i.e., hybrids).
*   **Reported Gross Debt:** €40.59 billion (€28.08 billion long-term + €12.51 billion short-term).
*   **Adjustments (Provisions/AROs & Cash):** S&P adds debt-like obligations such as Asset Retirement Obligations (AROs) and pension deficits to debt, while deducting accessible cash. ENGIE’s non-current provisions are €24.66 billion, and its cash and cash equivalents stand at €15.57 billion. 
*   **TAC Approximation:** €39.28B (Equity) + €40.59B (Debt) + €24.66B (Provisions) - €15.57B (Cash) = **~€88.96 billion**.

ENGIE’s currently outstanding hybrid bonds amount to **€3.39 billion**. 
Calculating the proportion of hybrids within the TAC gives us: 
€3.39 billion / €88.96 billion = **~3.81%**. 

**2. Refinancing & Capital Needs:**
Looking at ENGIE's cash flows for 2022, the company generated strong operating cash flows of €8.58 billion, which comfortably covered its capital expenditures (Purchases of Property, Plant, and Equipment) of €6.38 billion. Moreover, ENGIE actively executed net debt repayments (repaying €10.97 billion while borrowing only €8.67 billion) and retired €374 million of its existing perpetual notes during the year. These trends clearly indicate *moderate funding needs* rather than transformational M&A requirements or high refinancing constraints. 

**3. Leverage and Rating Headroom:**
ENGIE’s EBITDA is robust. Approximating from a current operating income of €4.3 billion + €5.1 billion in D&A + €2.7 billion in impairments, their EBITDA stands well over €12 billion against a net adjusted debt of ~€49.6 billion. The corresponding leverage ratio (~3.7x to 4x) yields strong rating headroom. There is minimal pressure requiring capital structure optimization via heavy hybrid reliance, providing a "mild leverage optimization rationale." 

**4. Cost of Debt:**
Given the 2022 market data, standard corporate bond yields sit at ~1.085%, whereas the sub-senior delta for non-financial IG is elevated at ~2.295%. Adding new hybrid bonds in this macro environment would tangibly increase ENGIE's current weighted average cost of debt, disincentivizing them from maxing out hybrid capacities unless strictly necessary.

**Conclusion:**
ENGIE's current hybrid structure aligns accurately with the ~3.8% mark, and its strong operational cash flows, solid IG rating preservation, and net-debt reduction trends perfectly check the boxes for a 3.75% threshold recommendation.

<answer>3.75%</answer>