30-year cumulative projection

Why this matters

Property tax is often treated as a background expense — a line item on a monthly mortgage statement that gets paid via escrow and forgotten. But over the lifetime of a home, it adds up to one of the largest costs of ownership, often exceeding the original purchase price by year 25 or 30. Projecting the total forces the cost into view and makes apples-to-apples comparisons across states, properties, and ownership horizons possible.

At a 3% annual growth rate, a $7,500 property tax bill today becomes $17,664 in year 30. The cumulative total over those 30 years exceeds $356,000 — money that goes to local services, schools, and infrastructure but doesn't build any equity for you.

Cumulative = Current × [(1 + g)^n − 1] / g

Where the growth comes from

Two engines drive year-over-year property tax growth:

• Reassessment — when assessed value rises with the housing market, the same mill rate produces a higher bill
• Mill rate increases — when local taxing authorities pass budgets that require higher rates, even unchanged assessed values cost more

In hot housing markets, reassessment dominates — Florida and Texas homeowners have seen 8–15% annual reassessment growth in recent years before caps kick in. In slower markets, mill rate growth is more visible — Pennsylvania and Ohio rural counties might see assessed values flat for years while school millages climb steadily.

Caps that flatten the curve

Several states limit how fast assessed values (and therefore tax bills) can grow:

• California (Prop 13): 2% per year cap on assessed value, until sale
• Florida (Save Our Homes): 3% or CPI per year cap on homestead
• Texas: 10% per year cap on homestead assessed value
• Michigan (Headlee/Proposal A): 5% or CPI per year cap on taxable value, until sale
• Oregon (Measure 50): 3% per year cap on taxable value

These caps dramatically reduce the cumulative-tax curve for long-term homeowners. A California homeowner who bought in 2005 has compounded assessed value at 2% for 20 years; a recent buyer down the street reset to current market and pays vastly more on the same house.

Picking the right growth rate

Different sources support different growth assumptions:

• 3% (default) — long-run national average, roughly tracking CPI plus modest real growth
• 2% — California with Prop 13 protection, conservative scenarios
• 4–5% — high-growth Sun Belt markets without caps, recent decade in TX, FL, GA, NC
• 1–2% — mature, slow-growth markets with stable mill rates and modest appreciation

For planning purposes, 3% is a defensible base case in most of the country. Try the calculator at multiple rates to bracket your uncertainty.

Worked examples

Example 1 — Average US homeowner, 30 years. Current annual property tax $7,500 at 3% growth:

• 5 years cumulative: ~$39,810
• 10 years cumulative: ~$85,960
• 20 years cumulative: ~$201,490
• 30 years cumulative: ~$356,750
• Year 30 annual tax: ~$17,664

Example 2 — High-tax state, 20-year hold. NJ homeowner with $14,500 current annual tax, 2.5% growth (Northeast typical):

• 10 years cumulative: ~$162,800
• 20 years cumulative: ~$370,500
• Year 20 annual tax: ~$23,700

Over a 20-year ownership, the cumulative property tax exceeds what most homeowners pay in mortgage interest at current rates.

Example 3 — Capped state benefit. Florida homestead with $4,200 current tax, 3% Save Our Homes cap (the cap itself, not the underlying market):

• 30 years cumulative: ~$199,800
• Same homeowner without the cap (assume 6% market growth): ~$331,000
• Cap-driven savings over 30 years: ~$131,000

The cap is one of the most valuable features of Florida (and similar states') tax structure — and it's automatic for homestead-qualified properties. Use this calculator with your cap rate to see the long-term impact.

Common mistakes

• Using the wrong starting bill. Use your most recent full-year bill, including all special assessments and district taxes — not just the headline number on your mortgage statement.
• Picking too low a growth rate. Optimism feels good but underestimates cumulative cost dramatically. A 1% underestimate over 30 years compounds to ~30% understatement of cumulative tax.
• Ignoring caps. If your state caps assessed value growth (CA, FL, TX, MI, OR), use the cap rate, not the market rate. The whole point of the cap is to suppress your growth curve.
• Forgetting that mill rates can fall. Some jurisdictions roll mill rates down after major reassessments to keep revenue neutral. Net growth can be lower than the assessment-only growth suggests.
• Treating "lifetime" as 30 years. Most homeowners don't stay in one home 30 years. Project for your actual horizon — often 7–15 years.

Frequently asked questions

What's a realistic long-run property tax growth rate?

Nationally, 2.5–3.5% is a defensible long-run average — roughly CPI plus modest real growth in housing values, balanced against occasional mill-rate cuts. Capped states (CA, FL, TX, MI, OR) run lower; uncapped fast-growth states (parts of GA, NC, TN, AZ, ID) can run higher.

Should I include inflation adjustments?

The 3% nominal growth rate already includes inflation. If you want real-dollar projections, subtract expected inflation (~2.5%) from the growth rate, leaving roughly 0.5% real growth. The cumulative will look much smaller in today's dollars.

How does the cumulative compare to mortgage interest over 30 years?

For a $400K mortgage at 7% over 30 years, total interest is roughly $560K. Property tax cumulative on the same home at ~$7,500/year and 3% growth is ~$357K. So mortgage interest typically exceeds cumulative property tax — but property tax lasts forever (you pay it after the mortgage is gone), and in high-tax states the comparison can flip.

Why would I project this?

Three reasons: (1) honest budget planning across a long ownership horizon, (2) comparing total cost of ownership across states or counties, (3) deciding when relocation math actually pencils out (a $5,000/year delta becomes $230,000+ over 30 years at 3% growth).

Does this projection account for selling and rebuying?

No — it assumes you hold the same home throughout. Selling and rebuying typically resets your assessed value to current market, often raising your starting bill substantially in capped states. Project per-home, then sum if you anticipate moves.

How can I reduce my projected cumulative tax?

Three real levers: (1) claim every exemption, (2) appeal successfully even once early in your ownership (savings compound), (3) relocate before the next 30-year cycle. The first two are no-regrets; the third is a lifestyle choice.

Does this match what I'd see in a financial planner's projections?

Most financial planning software uses 2.5–3.5% for property tax growth as a default. Some use a fixed nominal dollar escalation (e.g. +$200/year) instead of percentage growth — that approach undercounts in high-growth markets and overcounts in flat markets. Percentage growth is more defensible for long horizons.