Let’s analyze the situation step by step.

**1. Financial Performance and Position of Fortum**

- **Revenue** grew from €6,422M (2021) to €8,804M (2022), but much of this is likely driven by the energy crisis and high power prices, which may not be sustainable.
- **Comparable Operating Profit** was €1,871M (2022) vs €1,429M (2021), showing solid underlying performance.
- **Profit Before Tax** dropped from €4,332M to €455M, and **Net Loss** was massive (€-10,290M in 2022 vs €-114M in 2021), driven mainly by **€11,302M loss from discontinued operations**, primarily the Uniper segment impairment/write-down.
- **Equity** declined sharply from €13,665M to €7,737M, largely due to the discontinued operations loss and OCI impacts.
- **Total Assets** shrank from €149.7B to €23.6B, mainly because of deconsolidation of the Uniper segment, which also removed massive derivative positions and debt.
- **Cash flow from continuing operations** was €2,104M (2022), up from €1,119M (2021), indicating solid cash generation from the core operations.
- **Investing activities** showed a net inflow of €1,464M (2022), largely from divestments.
- **Financing activities** showed a net outflow of €4,686M, driven by debt repayments and dividends.

**2. Capital Structure and Leverage**

- Post-Uniper, the balance sheet is much smaller and less leveraged in gross terms.
- **Equity attributable to parent** is €7,670M; **noncontrolling interest** is minimal (€67M).
- **Financial liabilities** (current + noncurrent other financial liabilities) are significant: €3,658M (noncurrent) + €4,127M (current) = ~€7,785M, plus derivatives, but net debt is manageable given cash of €3,919M.
- Retained earnings fell sharply due to the loss, but **Issued Capital** (€3,046M) is stable.
- There’s no explicit mention of existing hybrid bonds, but the equity structure doesn’t show hybrid instruments separately. Given Fortum’s history, it has issued hybrids before, but the current capital structure seems to consist of straight equity and debt.

**3. Rationale for Hybrid Issuance**

- **Refinancing needs:** Fortum repaid significant debt in 2022 (€5,888M noncurrent repayments vs €2,421M proceeds). It still has debt maturities ahead, but the cash position is good (€3,919M liquid funds). The pressure is moderate.
- **Capex:** Investing capex was €534M in 2022, modest relative to size. No extraordinary growth capex is evident from the data.
- **Rating headroom:** The group’s equity base has been severely weakened by the Uniper loss, reducing the buffer for leverage metrics. Adjusted leverage may look elevated relative to the reduced equity.
- **Cost of debt:** EUR swap rates have risen sharply (5Y from -0.35% to 1.73%), corporate bond yields are higher (iShares Core Euro Corp ~1.09% avg 2022, sub-sen delta ~2.3%). Hybrids would be more expensive than senior debt, but not prohibitively so.
- **Dividends:** Proposed dividend of €0.91/sh (€817M total) indicates confidence, but also a cash outflow.

**4. Guideline Mapping**

Looking at the checklist:
- Fortum has **moderate refinancing needs** (debt repayments continue but are manageable).
- The equity base erosion might put **mild pressure on leverage metrics**, providing a rationale for some equity credit from hybrids to optimize the capital structure.
- The rating profile is under pressure post-Uniper, but the core operations are solid and cash-generative. It’s not in the "A" range strong anymore; likely BBB area, so hybrids can help maintain IG metrics.
- Cost of hybrid would be higher than current average debt cost, but not drastically.
- No indication that a massive hybrid program is needed for survival; rather, a moderate issuance would provide rating flexibility.

Therefore, a moderate level of hybrid issuance (around 3.75%–7.5% of adjusted capital) could make sense. Given the still-solid liquidity, manageable capex, and the need to partly cushion the equity decline for rating headroom, **3.75%** seems the most justified—providing mild leverage optimization without over-relying on expensive hybrid capital.

**Final Answer:**

<answer>3.75%</answer>