Let’s go through the workflow step-by-step.

---

**1. Identify the relevant industry**

Terna S.p.A. is the Italian electricity transmission system operator (TSO).  
- It is a regulated utility, operating under a national regulatory framework (ARERA in Italy).  
- It provides essential transmission infrastructure, and revenues are heavily tariff-based.  
Therefore, the most relevant methodology is **Regulated Utilities**.

---

**2. Estimate Adjusted Debt**

From the balance sheet (as of Dec 31, 2022):

**Reported debt** (both current and non-current borrowings):  
- Long-term borrowings: €8,416.7M  
- Short-term borrowings: €444.1M  
- Current portion of long-term borrowings: €1,909.3M  
Total reported debt = 8,416.7 + 444.1 + 1,909.3 = **€10,770.1M**

**Leases**:  
No explicit lease liability line. In IFRS, leases are often inside “Noncurrent financial liabilities” or “Other noncurrent liabilities”.  
Noncurrent financial liabilities = €247.2M (this may include derivatives, lease liabilities, etc.).  
Since no specific split is given, and given the lack of separate lease data, we assume zero lease adjustment for simplicity unless indication exists. We'll check for any debt-like items.

**Pension deficit**:  
Noncurrent provisions for employee benefits = €48.4M. This can be treated as debt-like. We include it.

**Guarantees**: No data on guarantees, assume zero.

**Hybrid debt portion**:  
They issued perpetual hybrid bonds: €989M (in equity).  
Per S&P methodology, 50% of hybrid is treated as debt until certain conditions. We’ll use the standard 50%: 0.50 × 989 = **€494.5M**.

**Other debt-like items**:  
- Other long-term provisions: €140.8M (some could be debt-like, but we’ll include them for conservatism).  
- Noncurrent financial liabilities could include derivatives, but without details we include them as debt.  

So total additions:  
- Pension deficit: 48.4  
- Hybrid portion: 494.5  
- Other long-term provisions: 140.8  
- Noncurrent financial liabilities (already included above in reported debt? We already counted them as debt-like, but they’re in borrowings/financial liabilities; no double counting.)

We’ll structure it as:  
Adjusted Debt = reported borrowings + pension provisions + other long-term provisions + hybrid portion – eligible cash.

**Eligible cash**:  
Cash and cash equivalents = €2,155.1M. We’ll assume all is eligible unless stated otherwise.

**Adjusted Debt** =  
10,770.1 (reported debt)  
+ 48.4 (pension deficit)  
+ 140.8 (other long-term provisions)  
+ 494.5 (50% hybrid)  
− 2,155.1 (cash)  
= **€9,298.7M**

---

**3. Estimate Adjusted EBITDA**

From income statement:

We can reconstruct EBITDA:  
Profit/loss from operating activities = €1,333.5M  
Add back D&A: €725.7M  
This gives EBITDA = 1,333.5 + 725.7 = **€2,059.2M**.

Adjustments:  
- No operating leases given → no lease adjustment.  
- Nonrecurring gains/losses: Not specified; we assume zero.  
- Pension adjustments: S&P would adjust operating expense to reflect service cost only; here, given detail, no adjustment possible. Assume zero.  
- JV proportional EBITDA: Associates’ profit/loss reported below operating profit, small amount (–€1M). We ignore.  
- Other normalization: None apparent.

**Adjusted EBITDA ≈ €2,059.2M**.

---

**4. Calculate the ratio**

Adjusted Debt / Adjusted EBITDA = 9,298.7 / 2,059.2 ≈ **4.52**.

---

**Final answer**:

<answer>4.52</answer>