Home Equity

Home equity is the home's market value minus every lien against it: the part of the house the owner actually owns. A $500,000 home with a $320,000 mortgage carries $180,000 of equity. The number builds through two engines: the amortization schedule converting payments into ownership, and appreciation raising the value side of the subtraction.

Equity is also the least liquid asset most families hold. Accessing it means borrowing against the house, through a home equity line of credit, a home equity loan, or a cash-out refinance, and lenders cap the borrowing at roughly 80% loan-to-value combined. The equity is the collateral, which is why borrowing it for consumption is borrowing the house.

The arithmetic is a subtraction with two moving parts. The value side rises with the local market: a 3% annual appreciation on a $500,000 home adds $15,000 of equity in the first year without a dollar of extra payment. The lien side falls with amortization: on a $320,000 mortgage at 6%, the first year of payments converts roughly $3,900 to principal, and the conversion accelerates as the schedule matures. The two engines compound: year ten of the same loan converts roughly $8,400, and the appreciation has compounded on top.

The borrowing side is capped. Lenders allow combined loan-to-value of roughly 80%: on the $500,000 home with $320,000 owed, total secured borrowing tops out near $400,000, leaving $80,000 of accessible equity through a line of credit, a loan, or a cash-out refinance. Each access is new debt at a new rate, secured by the house, and the 2006-2008 wave of cash-out borrowing is the reference case for treating the house as an ATM.

The tax angle changed in 2017. Interest on home equity debt is deductible only when the proceeds buy or substantially improve the home that secures it; interest on a line of credit spent on a car or a wedding is not, regardless of what the interest statement implies. The deduction follows the use of the funds, which the IRS states plainly and most borrowers never read.

Home equity is the net worth engine for most American families: the Federal Reserve's Survey of Consumer Finances puts housing at roughly a quarter of household assets, more than any other category. The equity is also undiversified, leveraged, and illiquid, which is the honest description of the largest asset most people own. It builds quietly through amortization and loudly through appreciation, and it disappears quietly in a downturn that hits both.

I watched a colleague named Brent (yes, that Brent) open a $60,000 line of credit against his house for a boat, in 2006, at the top of the market. The boat depreciated, the house fell 25%, and the equity that had funded the toy was the collateral the lender called. The line of credit survived; the equity did not.

The highest-leverage thing most Americans can do is let amortization and appreciation compound, borrow equity only for the house itself or genuine emergencies, and check the build with the home equity HELOC calculator. The mechanics of the access product are in the HELOC entry, and the paydown engine is in the mortgage amortization entry.