You’ve probably been told an appraisal is the objective number — the one the bank trusts, the one negotiations hinge on. In practice, it’s an educated estimate from a single person on a single day, and study after study shows that two licensed appraisers looking at the same property routinely arrive at values tens of thousands of dollars apart. The number on the report is more discretionary than the official tone suggests.
The methodology has built-in subjectivity
Most residential appraisals use the sales comparison approach: find three to five recently sold homes nearby, adjust for differences, and triangulate a value. Every step requires judgment. Which comps count as comparable? How much should you add for an updated kitchen, a finished basement, or a bigger lot? The Uniform Standards of Professional Appraisal Practice gives appraisers latitude on these adjustments, and Fannie Mae’s review data shows the same property can swing 5 to 10 percent based on which comps an appraiser chooses. That’s $30,000 to $60,000 on a half-million-dollar home — not a rounding error.
Bias and pressure are documented problems
Federal investigations have repeatedly found that appraisers undervalue homes owned by Black and Hispanic families compared to identical homes owned by white families. A 2022 Freddie Mac study confirmed the gap at the census-tract level. Beyond racial bias, there’s commercial pressure: appraisers who consistently come in low risk losing referrals from lenders and brokers, and those who come in high risk regulatory scrutiny. The result is a profession that’s nominally independent but practically incentivized toward whatever number keeps the deal alive — which is usually right at or just above the contract price. When the contract price is unrealistic, the appraisal often follows it instead of correcting it.
Automated valuations aren’t necessarily worse
Zillow’s Zestimate and similar AVMs (automated valuation models) get mocked, but their median error rates are now within a few percentage points of human appraisals on typical suburban homes. Where AVMs struggle is unusual properties — custom builds, rural land, anything without good comps — and where they shine is consistency. The same algorithm produces the same number twice, which human appraisers demonstrably don’t. Lenders are increasingly using “appraisal waivers” backed by AVMs for low-risk transactions, partly because the data shows the trade-off in accuracy is small and the cost savings are real.
The takeaway
Treat an appraisal as one data point, not a verdict. If a number comes in lower than expected and kills your deal, you have the right to request a reconsideration of value with better comps — and you should use it. If you’re refinancing and the appraisal seems generous, don’t assume it’ll hold next time. If you’re buying, run an AVM check yourself before the appraisal arrives so you can spot a wildly outlying number. The professional credential adds rigor, but it doesn’t eliminate the inherent variability in valuing something as idiosyncratic as a home. Knowing where the soft spots are is how you avoid being surprised by them.
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