Zillow Says $310K, Your Agent Says $280K. Who Is Right?

Neither, usually. A $30,000 spread on a house in that range is about 10% of the midpoint — and if your required profit on the deal was $40,000, that disagreement is three quarters of your margin. It is not an academic question.

The mistake is treating it as a question about which source to trust. Both are outputs. The evidence is underneath them.

What each source is actually good at

An automated valuation model is fast, covers everything, and has no stake in your decision. It is at its best on homogeneous housing stock with lots of recent sales — a subdivision where the houses really are interchangeable. It is a genuinely useful outlier alarm: if your number and the AVM are $60,000 apart, one of you should explain why before anyone writes an offer.

It is blind to the inside of the house. It does not know about the failing foundation, the addition without permits, or the kitchen someone finished last month. It also lags: it learns from closed sales, so it does not know what went under contract this week at a price nobody has seen yet.

If you want an error figure, look up the publisher's own disclosed accuracy for your county — most publish it — rather than repeating a national median that describes a different housing market than yours.

An agent's CMA knows things no model can. The agent has been inside comparable houses, knows which of them showed badly, knows the buyer pool for that price band, and knows what is pending right now.

It also carries incentives. A number produced to win a listing tends to run high; a number produced to help a friend win a bid tends to run low. This is not cynicism, it is just something to price in — and the way you price it in is by asking for the comps rather than the conclusion.

Reconcile the comp sets, not the numbers

Averaging $310,000 and $280,000 to get $295,000 is not analysis. It is splitting a difference you have not explained. Ask both sources for the sales underneath, and the gap almost always resolves into one of three things.

Different comp set. The model pulled everything in the subdivision, including three sales from the newer phase built two decades after your subject. The agent hand-picked four.

Different condition assumption. The agent's four comps were all original-condition houses — so the $280,000 describes an unrenovated house. The model made no condition adjustment at all, so the $310,000 describes an average house. Your subject after renovation is neither of them.

Different timing. The model is working from closed sales. The agent knows about two pendings that will close $15,000 above the last closed comp.

Worked example (hypothetical). Once you separate the sets, the useful subset is renovated sales in the same phase in the last six months. Suppose there are two, both around 1,600 sq ft: one closed at $296,000 ($185/sq ft) and one at $312,000 ($195/sq ft). Your subject is 1,580 sq ft, renovated to the same standard:

• Low end: 1,580 × $185 = $292,300
• High end: 1,580 × $195 = $308,100

Call the ARV $300,000 — and now you can say exactly why, which neither original number let you do. The AVM was high because it averaged in a newer phase. The agent was low because every comp was original condition. Both were correct about the question they were answering.

When they disagree and you cannot explain it

Sometimes you pull both comp sets and the gap does not resolve. That is information too, and the honest reading is that your submarket is thinner or less homogeneous than you assumed.

In that case: widen the search carefully, weight the closed renovated sales most heavily, and underwrite to the low end. A deal that only works at the top of an unexplained range is a deal that depends on the disagreement resolving in your favour.

What to do instead of picking a side

Use the AVM as a screen and an alarm — it is excellent at telling you when to stop and check something, and it costs nothing.

Use the agent for what the model cannot see: interior condition of the comps, pendings, buyer behaviour in that price band, and how the house will actually show.

Use closed renovated comps, condition-adjusted, to set the number. Then write down the two or three sales your ARV actually rests on. If you cannot name them by address, you do not have an ARV — you have an opinion with a dollar sign in front of it.

Frequently asked questions

How accurate is an automated home value estimate?

Accuracy varies enormously by market and is usually published by county rather than nationally. Check the publisher's disclosed figure for your area — and remember that no AVM can see the inside of the house.

Why is the online estimate higher than my agent's?

Most often because the model averaged a broader set of properties, or because your agent's comps were all in a different condition class than the model's. Compare the two comp sets and the reason usually appears immediately.

Should I use an AVM for ARV?

Not as the source. Use it to sanity-check an ARV you derived from condition-adjusted renovated comps. If the two are far apart, find out why before you offer.

Is an appraisal more reliable than either?

An appraisal is one more opinion, produced under professional standards and for a specific lender's purpose. It is more defensible, not automatically more correct — and it can be challenged with better comps.

What if I only have two good renovated comps?

Two is thin but usable if they genuinely bracket your subject. Underwrite to the lower one, and say in your notes that the comp set is thin — so the next reader knows the number's real confidence.