The dynamics are classic for this type of market: inventories are low, mortgage rates are low and demand is high. All price ranges are on the rise with some at an even higher rate because the short supply is causing competition among buyers.
Another reason many homeowners' may have more equity is simply not staying current with what is going on in the market. In a recent FNMA study, it indicates that 23% of owners believe they have negative equity in their home when actually, it is 9%. 37% believe they have greater than 20% equity in their home when actually 69% of homeowners do.
Even if you're not planning to sell your home, knowing the value helps you understand your financial position better. Home equity debt up to a $100,000 limit is tax deductible and can be used for any purpose. Owner's commonly refinance to eliminate mortgage insurance, consolidate mortgages, pay off higher interest rate debt like credit cards or student loans or to buy out an ex-spouse's equity.
Be aware that an automated value model like Zillow Zestimates uses algorithms to determine a price and while it might be in the ballpark, AVM results may only be accurate about 20% of the time. A comparable marketing analysis or broker's price opinion will be more accurate due the subjective approach that will be used by an agent with personal experience in the area. An agent will consider factors like condition, floorplan, marketability and demand.