Which of the following has the biggest impact on cash flows?

Operational Expenditure (Opex) includes recurring costs that directly affect an organization’s cash outflows , such as energy, labor, and service delivery costs. Depreciation is non-cash.

Exact Extract from IAM – Asset Management: An Anatomy (v4), Section 2.3 – Financial Management:

“Operating expenditure (Opex) is a key factor in cash flow planning and often dominates lifecycle cost models.”