Let’s go through the reasoning step by step.  

**1. What S&P’s rule means**  
S&P Global Ratings caps the equity credit from hybrid bonds at 15% of total adjusted capital (debt + equity). If a company already has hybrid instruments close to or at that threshold, issuing more would not give additional rating benefit.  

**2. ENGIE’s hybrid situation**  
From the equity breakdown, we see “Deeply Subordinated Perpetual Notes” (the typical structure for hybrids) at:  

- End of 2022: €3,393 million  
- End of 2021: €3,767 million  

**3. Total adjusted capital**  
At end of 2022:  
- Total equity (including non-controlling interests): €39,285 million  
- Long-term borrowings: €28,083 million  
- Current borrowings: €12,508 million  

Total adjusted capital = €39,285m + €28,083m + €12,508m = **€79,876 million**.  

15% cap = **€11,981 million** maximum hybrid capacity for equity credit.  

**4. Current utilization**  
ENGIE’s €3,393 million hybrids represent only **4.2%** of total adjusted capital—well below the 15% cap.  

**5. Would they need more hybrids?**  
Given their significant capex, fluctuating earnings, and volatile rate environment (rising swap rates in 2022), hybrids can be attractive for preserving credit metrics while getting equity credit. However, they still have plenty of room under the cap before reaching the limit.  

**6. Conclusion on the fraction**  
The question is “To what extent should they utilize the cap?”—meaning what percentage of the allowed 15% cap is optimal. Given their current low hybrid ratio, significant investment needs, and the interest rate environment, fully using the cap (i.e., 100% of the allowable 15%) might not be needed immediately, but they would likely aim to retain flexibility to use a large portion. The most reasonable in a corporate finance context would be to target **75%** utilization to balance rating headroom and capital efficiency.  

<answer>75%</answer>