Missing Zestimate data: handle null values correctly

A missing Zestimate is not a zero-dollar home

If the source does not supply a Zestimate for a property, PropertiesAPI can return zestimate: null. Preserve that missing state. Replacing it with zero corrupts averages, changes sorting and can make a property appear worthless in a user interface.

PropertiesAPI returns Zillow estimates when available; it does not generate its own Zestimate. The asking price, Zestimate, rent Zestimate and assessed tax value are separate fields. A fallback that substitutes one for another changes the meaning of the data, even when it produces a more complete-looking table.

Keep the four common values separate

Choose a field based on the question your application answers. A sale listing price describes an asking price. A Zestimate is Zillow’s estimate. A rent Zestimate is a monthly rental estimate. A tax-assessed value belongs to an assessment context.

Render missing values explicitly

Use a null check when formatting numeric fields. In JavaScript, truthiness checks also treat zero as false. A null-aware formatter distinguishes missing data from a numeric value without deciding whether zero is sensible for a particular field.

const money = new Intl.NumberFormat("en-US", {
  style: "currency", currency: "USD", maximumFractionDigits: 0
});
function displayEstimate(value) {
  return value == null ? "Not available" : money.format(value);
}
// null -> "Not available"; 0 -> "$0"

Exclude missing values from calculations deliberately

For a portfolio summary, calculate an estimate only from rows with a supplied numeric value, and show how many rows were excluded. Do not describe the resulting total as a complete portfolio valuation if some homes have no estimate.

For comparisons between list price and Zestimate, require both fields. Save an explicit missing reason such as “estimate unavailable” instead of producing an infinite ratio, zero gap or misleading percentage. If you use a different valuation model, keep its name and output in separate fields.

Check identity and collection time before diagnosing absence

First confirm that the returned property is the intended home. Then inspect the collection timestamp and cache state. A cached response represents an earlier collection, so the current source page may differ.

A null field alone does not establish why it is missing. Avoid telling users that a property is ineligible, newly built or too unusual unless you have evidence. If the estimate is essential to a workflow, use an unavailable state and a manual review path. Repeated requests cannot guarantee that the source will supply a missing field.

Describe estimates accurately in your product

Label the estimate with its source and date. Do not label it as an appraisal or use the PropertiesAPI brand as though it produced the estimate. Your interface should make the difference between a source estimate and a verified transaction clear.

Include a missing-estimate example in integration tests. It is often more valuable than another fully populated fixture because it checks formatting, calculations, sorting and exports at the same time. The property endpoint documentation is the current reference for field availability and semantics.