Operating Expenses (OpEx)
The recurring costs of running a rental property — taxes, insurance, management, maintenance, utilities, HOA. Subtracted from effective income to get NOI. Excludes debt service and capital expenditures.
Operating expenses (OpEx) are the recurring costs of running and maintaining a rental property — the bills you pay to keep it income-producing. They're subtracted from effective gross income to calculate net operating income, so they directly shape a property's value and your return.
What counts as an operating expense
- Property taxes — often the single largest line, especially in high-tax states like Texas.
- Insurance — hazard, liability, and (where relevant) flood or wind coverage.
- Property management — typically 8–10% of collected rent if you don't self-manage.
- Repairs & maintenance — routine upkeep, turnover make-ready, service calls.
- Utilities — any the owner pays (water/sewer, trash, common-area electric).
- HOA / condo dues, landscaping, pest control, snow removal.
- Administrative — bookkeeping, legal, leasing/advertising.
What is NOT an operating expense
Three exclusions are critical to get right, because folding them in (or leaving them out) distorts NOI:
- Debt service (mortgage P&I) — that's financing, accounted for after NOI.
- Capital expenditures — a new roof, HVAC, or full renovation are capitalized, not expensed (though you should reserve for them).
- Income taxes and depreciation — those are the owner's, not the property's.
The operating expense ratio
Investors often track the operating expense ratio — OpEx ÷ effective gross income. For typical residential rentals it commonly lands around 35–50%, depending on taxes, age, and whether management is included. A ratio far below that is a red flag that some expenses (capex reserves, vacancy, management) were left out of the pro forma.
A worked example
| Expense | Annual |
|---|---|
| Property taxes | $7,200 |
| Insurance | $1,800 |
| Management (8% of $30k) | $2,400 |
| Repairs/maintenance | $3,000 |
| HOA | $600 |
| Total OpEx | $15,000 |
On $30,000 of effective gross income, that's a 50% expense ratio — leaving $15,000 of NOI before debt service.
Why accuracy matters
Underestimating OpEx is the most common way a rental pro forma lies. New investors routinely omit management, real maintenance, and capex reserves, producing an inflated NOI, cap rate, and cash-on-cash return. Underwrite expenses honestly — use actuals where available, realistic market figures otherwise — and a property's true profitability comes into focus. The cost of optimism here is a deal that cash-flows on the spreadsheet but not in your bank account.
Frequently asked questions
What's included in operating expenses for a rental?
Property taxes, insurance, property management, repairs and maintenance, owner-paid utilities, HOA dues, and administrative costs like bookkeeping and leasing. These are the recurring costs of running the property. They're subtracted from effective income to get NOI.
Is the mortgage payment an operating expense?
No. Debt service (mortgage principal and interest) is a financing cost, not an operating expense, and it's accounted for after NOI. Operating expenses are the costs of running the property itself. Capital expenditures and income taxes are also excluded from operating expenses.
What's a typical operating expense ratio?
For residential rentals, operating expenses commonly run about 35–50% of effective gross income, depending on property taxes, age, and whether management is included. A ratio well below that often signals the pro forma omitted real costs like management, maintenance, or capex reserves.