To estimate the Net Debt / EBITDA ratio for HERA S.P.A. at the end of 2022 using the S&P methodology, we follow these steps:

**1. Calculate EBITDA:**
EBITDA is typically defined as Profit/Loss from Operating Activities plus Amortization, Depreciation, and Provisions.
*   Profit/Loss from Operating Activities (2022): 533,800,000 EUR
*   Amortisation, Depreciation, and Provisions (2022): 667,100,000 EUR
*   EBITDA = 533,800,000 + 667,100,000 = 1,200,900,000 EUR.

**2. Calculate Net Debt:**
Net Debt is calculated as total financial liabilities minus cash and cash equivalents and current financial assets.
*   Noncurrent Financial Liabilities: 5,689,900,000 EUR
*   Noncurrent Lease Liabilities: 55,100,000 EUR
*   Current Financial Liabilities: 650,100,000 EUR
*   Current Lease Liabilities: 21,300,000 EUR
*   Total Gross Debt: 5,689,900,000 + 55,100,000 + 650,100,000 + 21,300,000 = 6,416,400,000 EUR.

*   Cash and Cash Equivalents: 1,942,400,000 EUR
*   Current Financial Assets: 77,700,000 EUR
*   Total Cash and Liquid Assets: 1,942,400,000 + 77,700,000 = 2,020,100,000 EUR.

*   Net Debt = 6,416,400,000 - 2,020,100,000 = 4,396,300,000 EUR.

**3. Calculate Ratio:**
*   Ratio = Net Debt / EBITDA
*   Ratio = 4,396,300,000 / 1,200,900,000 ≈ 3.6608

Rounding to reasonable decimal places, we get 3.66.

<answer>3.66</answer>