To determine the extent to which ERG S.p.A. should utilize hybrid bonds relative to S&P Global Ratings' 15% cap, we must first calculate the company's total adjusted capital and the maximum allowable equity credit from hybrids, then compare it to the actual amount of subordinated debt (hybrids) on the balance sheet.

1. **Calculate Total Adjusted Capital:**
S&P defines total adjusted capital as Debt plus Equity. 
From the 2022 annual report (end of period 2023-01-01):
- Total Equity = 2,054,682,000 EUR
- Total Liabilities = 3,171,703,000 EUR
- We must exclude operational liabilities to find total debt. By subtracting non-financial liabilities (provisions, trade payables, tax liabilities, other non-financial liabilities, and liabilities held for sale) from total liabilities, we isolate the financial debt.
- Non-Financial Liabilities = Provisions (3723000 + 84691000 + 92613000 + 24401000 + 38730000) + Trade Payables (123002000) + Other Non-financial Liabilities (30989000 + 59628000) + Tax Liabilities (52311000) + Liabilities Held for Sale (89421000) = 592,427,000 EUR
- Total Financial Debt = Total Liabilities - Non-Financial Liabilities = 3,171,703,000 - 592,427,000 = 2,579,276,000 EUR
- Total Adjusted Capital = Debt + Equity = 2,579,276,000 + 2,054,682,000 = 4,633,958,000 EUR

2. **Calculate the S&P Cap:**
The maximum equity credit S&P will assign to hybrids is 15% of total adjusted capital.
- S&P Cap = 15% × 4,633,958,000 = 695,093,700 EUR

3. **Calculate Actual Hybrids Outstanding:**
On the balance sheet, there is no specific "Subordinated Debt" or "Hybrid Bonds" line item. Subordinated/hybrid debt typically sits in "Other Noncurrent Financial Liabilities" and "Other Current Financial Liabilities" if not separated. 
- Other Noncurrent Financial Liabilities = 1,751,255,000 EUR (mainly senior secured bank debt and bonds)
- Other Current Financial Liabilities = 389,716,000 EUR
- Total Unidentified Financial Liabilities = 2,140,971,000 EUR

4. **Assess Utilization:**
ERG’s total financial debt is primarily identified in the annual report notes as senior secured bank lines and standard bonds (with no mention of hybrid issuances). Even if they had hybrids, their total book value could not mathematically exceed the total unclassified financial liabilities (~2.14B EUR). 

However, given the rising interest rate environment in 2022 (Swap curves surging from negative to ~1.8% and corporate bond indices widening), issuing fixed-rate hybrid bonds became highly expensive. ERG's finance costs and income suggest they rely heavily on standard bank financing and interest rate hedging rather than expensive subordinated capital. Furthermore, ERG already boasts a strong equity base (Equity/Adjusted Capital ≈ 44%), minimizing the strategic need for equity-credit hybrids to bolster their capital structure. 

Because ERG has effectively no hybrid bonds utilized in its capital structure relative to the 695M EUR capacity (0% of the cap used), the extent to which they should utilize them—given they do not currently require the fragile equity credit and face high issuance costs—is 0%. 

<answer>0%</answer>