The honest answer: a successful property tax appeal saves the typical US homeowner somewhere between $539 and $3,000 per year, and the savings recuruntil the next reassessment. Here's where those numbers come from, and a worked King County example.
What the data actually says
We pulled the most-cited national figures:
- Median annual savings: ~$539 for a successful appeal, per widely-cited research.
- Reported customer averages: $774–$1,346/year (Ownwell published an $774/year median in 2025 across reductions they secured; other services report higher ranges depending on their customer mix).
- High-end outcomes: $3,000+/year on higher-value homes or in higher-tax jurisdictions.
On the assessment side, the National Taxpayers Union Foundation puts the typical successful reduction at 8–20% off assessed value. Your dollar savings = (reduction in assessed value) × (your effective tax rate).
The King County math
King County's effective property tax rate is roughly 1.0% of true and fair value. So for a typical Seattle-area home:
| Home assessed value | 10% reduction | 15% reduction | 20% reduction |
|---|---|---|---|
| $600,000 | $600/yr | $900/yr | $1,200/yr |
| $1,000,000 | $1,000/yr | $1,500/yr | $2,000/yr |
| $1,500,000 | $1,500/yr | $2,250/yr | $3,000/yr |
| $2,500,000 | $2,500/yr | $3,750/yr | $5,000/yr |
These are annual savings. A win on your appeal carries forward as the new baseline value, so the savings compound across multiple years.
The compounding effect
Most coverage of property tax appeals understates the real value by quoting only the first-year savings. The lowered value becomes the baseline going forward. Even at a modest $1,000/year saving:
- Year 1: $1,000
- Cumulative 5 years: $5,000
- Cumulative 10 years: $10,000+
For a 1–2 hour investment to pull comps and file a one-page petition, the time-adjusted return is unusually high.
How likely is it to work?
Per the National Taxpayers Union, of homeowners who file:
- 40–60% win some reduction at the local board level nationally.
- With strong comparable-sales evidence, win rates trend higher.
- Only about 3–5% of homeowners file in the first place — most over-assessments simply go unchallenged.
When the math doesn't work
Appealing isn't worth the time in a few cases:
- Your assessment is already below market. If comparable sales support a value higher than your assessed value, leave it alone — the Assessor can adjust upward.
- The reduction would be small.If your evidence only supports a 3% reduction on a $500k home, that's $150/year. Probably still worth a one-page filing, but don't hire a paid service for it.
- You bought recently at full price.Your sale price IS the strongest comp — and it's on your side.
The first step: know your number
Before deciding whether to appeal, you need three pieces of data: your current assessed value, your assessment trajectory over the last few years, and the recent comparable sales near you. This site assembles all three for free, from official King County data, in 30 seconds. From there, the appeal decision is straightforward — and so is filing it.