To estimate the Net Debt / EBITDA ratio for Italgas S.p.A. for the year 2022 based on the S&P methodology, we proceed as follows:

1.  **EBITDA Calculation:**
    EBITDA is typically calculated as Operating Profit + Depreciation & Amortisation.
    *   Profit/Loss from Operating Activities (2022-01-01 to 2023-01-01): 641,338,000 EUR
    *   Depreciation, Amortisation, and Impairment (2022-01-01 to 2023-01-01): 479,186,000 EUR
    *   EBITDA = 641,338,000 + 479,186,000 = 1,120,524,000 EUR

2.  **Net Debt Calculation:**
    Net Debt is generally defined as Short-term Financial Liabilities + Long-term Financial Liabilities - Cash and Cash Equivalents. (Note: We use the 2023-01-01 values, which represent the end of the 2022 reporting period).
    *   Short-term Financial Liabilities (Excluding Other Current Financial Liabilities): 142,437,000 EUR
    *   Other Current Financial Liabilities: 290,000 EUR
    *   Long-term Financial Liabilities (Excluding Other Non-Current Financial Liabilities): 6,402,913,000 EUR
    *   Other Non-current Financial Liabilities: 34,000 EUR
    *   Total Gross Financial Debt = 142,437,000 + 290,000 + 6,402,913,000 + 34,000 = 6,545,674,000 EUR
    *   Less: Cash and Cash Equivalents (2023-01-01): 451,946,000 EUR
    *   Net Debt = 6,545,674,000 - 451,946,000 = 6,093,728,000 EUR

3.  **Net Debt / EBITDA Ratio:**
    *   Ratio = 6,093,728,000 / 1,120,524,000 ≈ 5.4382

Rounding to the standard financial presentation:

<answer>5.44</answer>