What Inflation Rate Should You Use for Expense Growth?

What inflation rate should you use for expense growth?

For most long-term rental underwriting, use 2.5–3% annual expense growth as your baseline. That range tracks the long-run trend of U.S. consumer inflation and is defensible enough to survive lender and partner scrutiny. But the smarter move is to stop treating "expenses" as one blob — different cost lines grow at different rates, and forcing all of them into a single number is where projections quietly go wrong.

Below is how an experienced underwriter thinks about expense inflation: what rate to pick, why a single blended figure misleads you, and the pitfalls that turn a "conservative" pro forma into an optimistic one.

Why one blended rate is the wrong mental model

When you type a single inflation rate into a pro forma, you're assuming taxes, insurance, maintenance, and management all rise in lockstep. They don't.

Over the last several years, many investors watched insurance premiums climb far faster than general inflation in coastal and wildfire-exposed markets, while property taxes jumped after reassessment — sometimes stepping up 10%+ in a single year, then flattening. Meanwhile, a fixed property-management contract might hold at 8% of collected rent for the entire hold.

If you blended all of that into one 3% assumption, you understated the fast-growing lines and overstated the flat ones. The netting can look fine — until the fast lines dominate your later years and crush cash flow right when you assumed it would be strongest.

The line-item approach

Split your operating expenses and assign each a growth rate:

• Property taxes — Grow at your state's assessment rules, not general inflation. In markets with caps (e.g., a fixed annual percentage limit on assessed value), model the cap. In markets that reassess to market on sale, model the post-purchase jump first, then the annual trend after. See Will My Property Taxes Go Up After I Buy? for how to handle that reset.
• Insurance — Historically volatile. In high-risk markets, stress-test 6–10%+ growth for the first several years rather than 3%. Read how much landlord insurance costs before you anchor on a low number.
• Maintenance & repairs — Tracks labor and materials, which have outpaced headline inflation in tight construction markets. Use 3–4%.
• Property management — Usually a percentage of rent, so it grows with your rent assumption, not a separate inflation figure. Don't double-count it.
• Utilities (if owner-paid) — 3–4%, higher in energy-volatile regions.

A concrete example

Take a single-family rental with these Year 1 operating expenses:

• Property taxes: $3,600
• Insurance: $1,400
• Maintenance: $1,800
• Management (8% of $24,000 rent): $1,920
• Other (utilities, misc.): $600

Blended 3% approach, Year 10: roughly $12,470 total operating expense.

Line-item approach, Year 10 (taxes at 2%, insurance at 7%, maintenance at 3.5%, management growing with 3% rent, other at 3%): roughly $13,300 — about 7% higher, driven almost entirely by insurance.

That $800+ gap in a single year is real cash. Multiply it across a hold and it can be the difference between a deal that clears your cash-on-cash return hurdle and one that doesn't.

Rules of thumb an experienced investor uses

• Default to 2.5–3% for the "soft" lines (maintenance, utilities, misc.) and model taxes and insurance separately.
• Never assume expenses grow slower than rent by default. If you inflate rent at 3% and expenses at 2%, your margins expand every year automatically — a subtle way to talk yourself into a mediocre deal. When in doubt, grow expenses at least as fast as rent.
• Front-load the volatility. Insurance and taxes tend to shock early (post-purchase reassessment, hard insurance market) then normalize. A flat rate misses the timing that matters most to your early-year cash flow.
• Match your appreciation and inflation assumptions. If you're using an aggressive appreciation rate in your analysis, pairing it with rock-bottom expense growth is internally inconsistent. Hot markets usually mean rising labor, insurance, and reassessment risk too.
• Stress-test the downside. Run the deal a second time at 4–5% blended expense growth. If it still cash-flows, you have real margin. If it flips negative, you've found your fragility.

The pitfalls that quietly wreck projections

Pitfall 1: Copying a default and forgetting it. Many calculators ship with a 2% expense inflation default. Leave it there and you may be underwriting a decade of costs at a rate reality hasn't matched in years.

Pitfall 2: Ignoring the tax reset. In reassessment-on-sale states, the biggest expense move happens in Year 1 — not from inflation at all — and no annual growth rate captures it.

Pitfall 3: Guessing insurance in a hard market. A 3% assumption on a premium that's actually climbing 8% compounds into a serious miss by Year 7.

Pitfall 4: Blending everything, then calling it conservative. "Conservative" isn't a bigger single number. It's modeling each line honestly and knowing which one breaks the deal.

Where real data beats a guess

Every number above — taxes, insurance, the local trend for maintenance costs — is a research task. Doing it by hand for each property is slow, and typing your best guess into a spreadsheet is exactly the garbage-in, garbage-out problem that makes pro formas untrustworthy.

This is where analyzing with live, verified data pays off. Tools like PropertyWiz AI pull current, market-calibrated figures for taxes, insurance, and inflation and pre-populate them — including a property-tax forecast that accounts for reassessment — so your expense-growth assumptions start from real data instead of a copied default, then stress-test the deal automatically.

Bottom line

Use 2.5–3% as your baseline for general operating expenses, but underwrite taxes and insurance as their own lines with their own growth paths. Never let expenses grow slower than rent without a reason, front-load the volatility, and run a higher-inflation stress case before you commit. The rate you pick for expense growth won't make a bad deal good — but the wrong one can hide a bad deal until it's yours.