The short answer
There are three real ways to find your home's value: an automated valuation model (Zillow's Zestimate, Redfin Estimate) which is free and instant but frequently off by 5% to 15% or more in a fast-moving market; a comparative market analysis (CMA) from a local agent, which is free, takes into account recent comparable sales and current market conditions, and is generally accurate within a few percentage points; and a licensed appraisal, which costs $400 to $600, takes several days, and is the only one of the three that's legally binding for a mortgage transaction.
For a rough sense of your equity, an automated estimate is fine. For anything involving an actual decision — listing, refinancing, or a major life event — a CMA or appraisal is the only method worth trusting.
Why Zestimate-style tools are especially unreliable in Las Vegas
Automated valuation models work by comparing your home to recent sales using public records and algorithmic pattern-matching — they don't know about a renovated kitchen, a view lot, a busy street, or a master-planned community premium like those found in Summerlin or Lake Las Vegas. Las Vegas also has unusually high variance in home age, lot premiums, and HOA-driven community differences packed into small geographic areas, which is exactly the kind of nuance automated models struggle with. Two homes three streets apart can have meaningfully different values that a Zestimate simply can't detect.
What a CMA actually looks at
A proper comparative market analysis pulls 3 to 6 recently sold homes as similar as possible to yours in square footage, lot size, age, condition, and — critically — the same or an adjacent neighborhood, then adjusts for differences (a renovated bathroom here, a smaller garage there). A good agent will also factor in active listings and pending sales, since those tell you where the market is heading, not just where it's been.
When an appraisal is worth the cost
Appraisals are required for most mortgage refinances and purchases, but they're also worth commissioning independently if you're settling an estate, going through a divorce, disputing a property tax assessment, or need a value that will hold up if challenged. Unlike a CMA, an appraisal follows a standardized methodology (USPAP) and is performed by a state-licensed appraiser, which gives it legal weight a CMA doesn't have.