To estimate the FFO / Net Debt ratio for ERG S.P.A. at the end of 2022, we first determine the Funds From Operations (FFO) and the Net Debt from the provided financial facts.

**1. Funds From Operations (FFO)**
FFO typically corresponds to the cash generated from operating activities before changes in working capital.
Looking at the data, the exact metric is directly provided:
* "Cash Flows From Used In Operations Before Changes In Working Capital" (2022-01-01 - 2023-01-01): 616,360,000 EUR.

**2. Net Debt**
Net Debt is generally calculated as Total Interest-Bearing Debt minus Cash and Cash Equivalents. Under standard IFRS reporting, total debt includes non-current and current financial liabilities measured at amortized cost (typically capturing bank loans and bonds) as well as lease liabilities. 
From the balance sheet as of 2023-01-01 (which represents the end of 2022):
* Other Noncurrent Financial Liabilities: 1,751,255,000 EUR
* Noncurrent Lease Liabilities: 150,955,000 EUR
* Other Current Financial Liabilities: 389,716,000 EUR
* Current Lease Liabilities: 6,362,000 EUR

Total Debt = 1,751,255,000 + 150,955,000 + 389,716,000 + 6,362,000 = 2,298,288,000 EUR

* Cash And Cash Equivalents: 392,811,000 EUR

Net Debt = Total Debt - Cash And Cash Equivalents
Net Debt = 2,298,288,000 EUR - 392,811,000 EUR = 1,905,477,000 EUR

**3. FFO / Net Debt Ratio**
Ratio = FFO / Net Debt
Ratio = 616,360,000 / 1,905,477,000 ≈ 0.3235

<answer>0.323</answer>