Appraisal vs. CMA vs. Zestimate: Which Home Value Can You Trust?

Look up your home online and you’ll see an estimate. Type the address into an AI assistant and it may build you a “CMA” with charts. Ask an agent and you’ll get a comparative market analysis. Hire an appraiser and you’ll get an appraisal. For the same house in Phoenix or the West Valley, those numbers are often different, sometimes by a lot.

Here’s what each one is, how it’s made and when it’s good enough.

Online estimates (Zestimate and similar)

What it is: an automated valuation model (AVM). A computer estimates value from public records, recent sales and listing data.

Strengths: free, instant and handy for tracking a rough trend.

Limits:

• It doesn’t see inside the home: no condition, updates, layout or problems.
• It relies on county records, which can have the wrong square footage, bedroom count or features.
• Different sites can give very different numbers for the same house.
• It isn’t prepared by a licensed person and isn’t accepted by lenders, courts or the IRS as an appraisal.

Good enough for: curiosity and rough planning.

Comparative market analysis (CMA)

What it is: a real estate agent’s opinion of a likely list or sale price, based on nearby sales and listings.

Strengths: free, and from someone who knows the local market and buyers.

Limits:

• It’s a sales tool. The agent may be competing for your listing.
• It isn’t prepared under appraisal standards, and the method and adjustments vary by agent.
• It often leans on active listings, which are asking prices rather than closed sales.

Good enough for: a starting point for a listing price, especially in a stable market.

AI-built CMAs (Perplexity, ChatGPT and similar tools)

What it is: a newer option. You type an address into an AI assistant and it pulls nearby sales from public web pages, picks “comps,” and produces a polished value range with maps and charts.

Strengths: fast and free or cheap. It’s a good way to see what has sold nearby.

Limits:

• The data isn’t verified. The tool reads whatever is on public websites and listing portals. It can’t confirm that a sale closed at that price, whether there were seller concessions, or whether it was a family or distressed sale.
• It doesn’t know the house. It can’t see condition, updates, an unpermitted addition or a busy-street location unless the web happens to say so, and county records are sometimes wrong.
• Comp choice and adjustments are a black box. A nice chart can hide sales that aren’t truly comparable.
• No one is accountable. There’s no license, no professional standards and no signature, so lenders, courts, the IRS and attorneys don’t accept it as an appraisal.

Good enough for: a quick look at the neighborhood before you talk to an agent or appraiser.

When you still need a certified appraisal: a date-of-death or estate value, probate, a divorce or co-owner buyout, a tax appeal, a PMI removal your servicer accepts, or any time the number has to stand up to someone else’s review.

Appraisal

What it is: an independent opinion of market value by a state-certified or licensed appraiser, following the Uniform Standards of Professional Appraisal Practice (USPAP).

How it’s made:

1. The appraiser inspects and measures the home (or, for an exterior-only report, states clearly what was relied on instead).
2. The appraiser chooses closed sales of similar homes and adjusts them for differences in size, condition, garage, pool, lot and updates.
3. The appraiser reconciles those adjusted sales to a value as of a stated effective date, which can be today or a past date.
4. Everything is explained in a written report.

Strengths: independent (the fee doesn’t depend on the value), documented and defensible.

Good enough for: taxes, estates and probate, divorce, co-owner buyouts, court, PMI removal (if your servicer accepts it), and pricing a sale when you want a number buyers’ appraisers are likely to support.

Which one do you need?

Situation	Usually enough
Just curious what it’s worth	Online estimate or AI tool
Choosing a list price with an agent	CMA, or a pre-listing appraisal if you want an independent check
Selling by owner (FSBO)	Pre-listing appraisal
Date-of-death value, estate or trust	Appraisal
Divorce or co-owner buyout	Appraisal
Property tax appeal	Appraisal can support it

Common questions

Why is my appraisal lower than the online estimate? The estimate can’t see condition and may rely on wrong records or on sales that aren’t truly comparable. An appraisal explains exactly which sales it used and why.

Can an appraisal be higher than a CMA? Yes. An appraisal follows the evidence. Sometimes a CMA prices low for a quick sale, and sometimes high to win a listing.

Does an appraisal cost more? Yes, unlike the free options. For decisions involving taxes, family or the court, it’s usually the one people rely on.

Get a value you can rely on

West Valley Appraisal Services prepares independent residential real estate appraisals for homeowners, sellers, executors and attorneys throughout Phoenix / Maricopa County, Arizona.

See pre-listing appraisals, market value appraisals, or call (602) 717-8450.

Written by Jason Clow, State Certified Residential Appraiser #21559. This article is general information, not legal, tax or financial advice.