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An honest comparison

ListPrep vs. a Zestimate, for Seattle homes

Both are automated estimates. One is a nationwide model; one is built only for Seattle, from King County’s own records. Here’s what each gets right — and which to use when.

The short answer: for a home that isn’t listed for sale — which is most homeowners checking their value — Zillow’s own published accuracy data shows a median Zestimate error around 7%. On a typical $1.2M Seattle home, that’s roughly ±$85,000. ListPrep narrows that for Seattle by using data the Zestimate doesn’t: the county’s grade and condition rating for your exact house, the land-vs-structure split of its assessed value, and five quick answers from you. And it shows every comparable sale and adjustment behind the number.
Comparison written July 2026. Zestimate figures are Zillow’s published medians; your mileage varies by home.
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What only ListPrep shows

The county’s own file on your home. Every King County home has an official construction grade and condition rating, a lot size, zoning, and an assessed split between land and structure. ListPrep puts that in your report; a Zestimate never shows it. In close-in Seattle neighborhoods the county often attributes 60–90% of a property’s value to the land alone — which changes what renovations are worth doing.

Your walk-away number. Washington sellers pay a graduated excise tax (1.1–3.0% by price tier), commissions, and closing costs. ListPrep computes the net — sale price minus every real cost — with a commission toggle for the post-2024 rules. A Zestimate stops at the sticker price.

Development upside. ListPrep checks your zoning and lot against Seattle’s ADU rules and prices the opportunity with real permit data (800 recent ADU permits, median ~$221K). Buyers pay premiums for that potential; most owners don’t know they have it.

A plan, not just a number. A ranked list of prep projects with costs calibrated against 2,600+ City of Seattle permits — and, just as important, the list of projects that don’t pay back before a sale.

What Zillow does better

Browsing homes for sale, rental data, national coverage, and photos of listed homes. If your home is outside King County, use Zillow — ListPrep won’t even try. Seattle-only is the point: depth over breadth.

Why a national model struggles here

Automated models are most accurate where housing is uniform. Seattle is the opposite: a 1906 Craftsman and a 2019 townhome can share a block, view premiums swing six figures within a hundred feet, and land — not structure — carries most of the value. That’s exactly the information sitting in county records, which is why ListPrep starts there.

Frequently asked questions

Is ListPrep more accurate than a Zestimate for Seattle homes?

For off-market homes, Zillow’s published median error is around 7% — roughly ±$85,000 on a $1.2M home. ListPrep narrows that for Seattle using county records and your condition answers, and shows every comp and adjustment behind the number.

What does ListPrep show that Zillow doesn’t?

The county’s grade and condition for your home, the land-vs-structure value split, your after-tax walk-away number, ADU development potential, and a permit-calibrated prep plan with a skip list.

When is Zillow the better tool?

Anywhere outside King County, and for browsing listings or rentals. ListPrep is Seattle-only by design.

Keep going

Seattle home values by neighborhood County-record medians See a full sample report What you get How home values are calculated Understand your number
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Zestimate® is a registered trademark of Zillow, Inc. ListPrep is not affiliated with Zillow. Both tools produce automated estimates, not appraisals.