Three estimators give three different numbers for the same Claremont house because each one is a separate automated valuation model (AVM), a computer program that predicts value from property records and nearby sales, and each reads its own data, picks its own comparable sales and refreshes on its own schedule. None of them has been inside the house. The spread between them tells you how hard the house is to read from a desk. It does not tell you which number is right, and none of the three is an appraisal.
This article is part of the online estimates vs. appraisals series. It takes the short answer in how to judge home value estimator results for a Claremont house and follows it through, input by input.
What does each estimator say it reads?
Each provider describes its own method. These pages were opened on November 6, 2026.
EstimatorWhat its own page says it usesWhat its own page says about itself
Redfin Estimate
"We use MLS data on recently-sold homes to calculate your property's current market value." It looks "for nearby homes that have recently sold and have similar features."
"Like other estimates, the Redfin Estimate is not a formal appraisal or substitute for the in-person expertise of a real estate agent or professional appraiser."
Opendoor estimate
"Our automated valuation model uses available property data and comparable homes to estimate a value range."
"It does not inspect your home or collect details about its current condition."
HomeLight estimator
It "combines details you share about your home with data pulled from public records like MLS data," with "a short questionnaire that accounts for your home's property type and condition."
Its estimates are "only approximations, not formal appraisals."
Zestimate
Zillow's Zestimate page refused automated reading on November 6, 2026, so it is not quoted here.
Read Zillow's own Zestimate page for its description.
HomeLight states the reason in one line: "different websites use different algorithms, data sources, and weighting methods."
Where do the three numbers part ways?
1. The inputs are not the same
One model leans on listing data, another on the public record, the facts the county holds about a parcel such as recorded building area, lot size, year built and recorded sales, and a third adds what the owner types into a questionnaire. On an older Claremont house these sources often disagree. A Craftsman near the Colleges whose back porch was enclosed decades ago may carry one gross living area, the finished, heated space above grade, in the record and another in an old listing. Each model starts from whichever figure it holds.
2. Each one picks its own comparable sales
A comparable sale is a closed sale of a similar house that a buyer of the subject would have weighed. Each model chooses its comparables by its own rules, and most do not show you all of them. For a postwar ranch house north of Foothill Boulevard, where the tracts repeat a handful of layouts, the rules tend to land on similar sales. For a Claraboya or Padua Hills home, where few similar sales happen nearby, one model may reach downhill to flat tracts and another may reach east across Mills Avenue into Montclair, a different county. When Montclair sales leak into a Claremont estimate follows that second case.
3. They refresh on different days
Redfin says its estimate "is updated daily for homes that are for sale, and weekly for those that are off the market." Other providers keep their own schedules. On the day you compare them, each may reflect a different set of recent sales, so the gap can open or close with no change to the house.
4. One may carry the owner's edits and another may not
Redfin lets an owner edit home facts or create an "Owner Estimate that will allow you to select your own comparable homes." An edit on one portal does not travel to the others. Correcting home facts on a portal explains what an edit changes and what it does not.
What is the spread telling you?
A narrow spread usually means the data describes the house the same way to every model: a common floor plan, a recent sale nearby, records that match the house. A wide spread usually means the house is hard to read from a desk. In Claremont that is the pre-1940 house with later additions near the Village, the Village expansion infill with a short sales history, the hillside home, and the lot with a rear unit, covered in what an AVM misses on a permitted ADU.
Two habits do not help. Averaging the three numbers mixes three unseen sets of comparables into a fourth number with no evidence behind it. Picking the number you prefer is the same problem with a preference added. Each tool's confidence range, the spread of values within which the model expects the price to fall, belongs to that model alone; reading the stated error range covers what those ranges mean.
The same house, seen by an appraiser
An appraisal is an opinion of value, the conclusion about market value a licensed or certified appraiser develops and signs as of an effective date, the date the opinion applies to. The questions that split the three estimators have one written answer in a report.
QuestionThree estimatorsAn appraisal
Who has seen the house?
No one
The appraiser, in most assignments
Where does living area come from?
Whichever record each model holds
Measured on site
Which sales were used?
Each model's own, often not shown
Named in the report, each with its adjustments explained
What date does the number apply to?
The day you looked
A stated effective date
Who may rely on it?
Redfin and HomeLight say theirs are not formal appraisals
The intended users, the people entitled to rely on the report
The comparable grid in the report shows the work. Every figure in an example on this site is a dash, because the reasoning, not a number, is the point. The pillar, what an online estimate cannot see in Claremont, sets out the full blank grid.
Four numbers that are not appraisals
An automated estimate, from any of the three tools, is not an appraisal. An agent CMA, the comparative market analysis a licensed real estate agent prepares to suggest a list or sale price, is not an appraisal. A county assessment, the taxable value the Los Angeles County Office of the Assessor sets for a Claremont parcel under California's assessment rules, is not an appraisal. A cash offer, the price a buyer will pay on stated terms, is not an appraisal. The appraisal vs. estimate page sets all five numbers side by side.
Next step
If a lender, a court, a trustee, a CPA or an appeals board will read the value, they will expect an appraisal with an effective date and a named set of comparable sales. The Claremont area page describes the pockets that split estimators most. You can request an appraisal or call (909) 324-6122. The fee is set by the scope of the assignment and quoted before work begins, and it does not depend on the value.
Sources
- Redfin, Redfin Estimate (MLS data, comparable selection, update schedule, Owner Estimate, not a formal appraisal; page marked "Last updated 11/05/26") (accessed November 6, 2026)
- Opendoor, home value estimator (automated valuation model; does not inspect the home) (accessed November 6, 2026)
- HomeLight, home value estimator (why estimates differ; approximations, not formal appraisals) (accessed November 6, 2026)
- Zillow, Zestimate page (attempted November 6, 2026; the page refused automated reading, so it is not quoted)
- Los Angeles County Office of the Assessor (accessed November 6, 2026)
- The Appraisal Foundation, Uniform Standards of Professional Appraisal Practice (USPAP), 2024 edition (accessed November 6, 2026)
- California Bureau of Real Estate Appraisers, license lookup for Gordon Hall (accessed November 6, 2026)
Gordon Hall, California Certified Residential Real Estate Appraiser, BREA No. AR003877 (lookup: https://www2.brea.ca.gov/breasearch/faces/party/view.xhtml?id=23601). Reports are prepared in conformity with the Uniform Standards of Professional Appraisal Practice (USPAP). Nothing here is legal or tax advice; admissibility is always the court's decision.
Frequently asked questions
Why does my house have three different online values?
Each online value comes from a separate automated valuation model. Each reads its own mix of listing data, public records and owner answers, picks its own comparable sales by its own rules, and refreshes on its own schedule. HomeLight's page puts it this way: different websites use different algorithms, data sources and weighting methods. None of the three is an appraisal.
Which of the three estimates should I believe?
None of them is evidence of market value on its own, and this site does not rank them. A narrow spread suggests the data describes the house consistently; a wide spread suggests the house is hard to value from a desk. If someone else must rely on the value, such as a lender, a court, a trustee or a CPA, they expect an appraisal.
Can I average the three numbers to get a better value?
No. Averaging mixes three unseen sets of comparable sales and three sets of inputs into a fourth number with no evidence behind it. An appraisal names the comparable sales it used, explains each adjustment and states the effective date, the date the opinion of value applies to.
Why are the numbers further apart on some Claremont houses than others?
Houses that are easy to read from records, such as postwar ranch houses north of Foothill Boulevard with repeated floor plans, tend to draw closer numbers. Pre-1940 houses with later additions near the Village, hillside homes in Claraboya and Padua Hills, lots with a rear unit and houses near the Mills Avenue county line tend to draw them apart, because the models choose different sales for them.
