To determine the appropriate level of hybrid bond issuance for ENGIE, we must analyze its financial metrics, existing capital structure, market conditions, and strategic needs based on the provided 2022 annual report data and the S&P methodology framework.

1. **Existing Hybrid Capital & Adjusted Capital Calculation**:
   ENGIE already has a significant amount of hybrid capital in the form of "Deeply Subordinated Perpetual Notes." As of Dec 31, 2022, this stands at €3.393 billion (€3,393 million). 
   To calculate the total adjusted capital, we sum the total equity and adjusted debt. Total Equity at year-end 2022 is €39.285 billion. Total debt (financial debt) is the sum of Long-term Borrowings (€28.083 billion) and Current Borrowings (€12.508 billion), totaling €40.591 billion.
   Total Adjusted Capital = Equity + Adjusted Debt = €39.285B + €40.591B = €79.876 billion.
   The current hybrid proportion is €3.393B / €79.876B = **4.25%**.

2. **Financial Performance and Leverage Pressure**:
   2022 was a challenging year for ENGIE's income statement, largely due to impairments and derivative valuations. Profit Loss from Continuing Operations was -€1.793 billion, and Net Financial Income Loss was -€3.003 billion. However, operating cash flow remained robust at €8.586 billion. Despite the net loss, cash taxes were negative (income), and the company maintained solid cash generation. Yet, the net loss significantly reduced retained earnings and compressed the equity base (Total Equity dropped from €41.98B in 2021 to €39.28B in 2022). This deterioration in credit metrics and compression of the equity base implies that leverage has likely increased, creating a rationale for capital structure optimization to stabilize leverage metrics.

3. **Capital Expenditure & Refinancing Needs**:
   ENGIE has moderate to high capex needs, with net purchases of PPE and intangibles reaching €6.379 billion in 2022 (up from €5.99B in 2021), reflecting the ongoing energy transition investments and transformational capex programs typical for utilities shifting towards renewables. Furthermore, the company has sizeable refinancing needs, with current borrowings and the current portion of noncurrent borrowings at €12.508 billion and long-term borrowings at €28.083 billion, alongside massive derivative liabilities that require robust capital buffers to manage.

4. **Rating Profile & Investment Grade Preservation**:
   Utilities like ENGIE typically target strong Investment Grade ratings ("A" range) to fund large infrastructure pipelines. The compression in equity and volatile earnings from continuing operations (-€1.96B attributable to owners) puts pressure on leverage headroom. Issuing hybrid bonds—especially since ENGIE already carries them and understands the market—would be an efficient way to optimize adjusted leverage metrics (as S&P treats qualifying hybrids as 50% equity under their methodology) while avoiding the dilution of common equity. 

5. **Cost of Debt and Market Conditions**:
   In 2022, the swap curve shifted significantly higher (5Y average 1.726%), and corporate bond yields (iShares Core Euro Corp Bond) averaged 1.085%, while subordinated (Sub-Sen) yields were around 2.295%. Given the rising rate environment, the cost of hybrid debt will increase the current cost of debt, but it remains a manageable and marginal impact relative to the benefit of maintaining IG stability and funding long-life assets with matching perpetual/equity-like capital.

6. **Guideline Mapping**:
   - The 4.25% existing hybrid level puts ENGIE naturally between the 3.75% and 7.5% thresholds.
   - The rationale fits the **7.5%** description: Moderate acquisition/refinancing needs, rating headroom moderately constrained by 2022 earnings volatility, hybrid issuance meaningfully improves adjusted leverage metrics, and the cost of hybrid slightly increases the current cost of debt. 
   - An issuance of roughly €2.5 billion to €3 billion (within the €3B/year limit) would bring the hybrid ratio to around 7.5% (€3.393B + €2.6B ≈ €6B / €82B pro-forma capital), perfectly aligning with the target to stabilize leverage and support the ongoing heavy capex pipeline without over-levering the balance sheet.

Therefore, targeting a 7.5% total adjusted capital allocation to hybrids provides the right balance of equity credit optimization and funding flexibility.

<answer>7.5%</answer>