Equity is the difference between what you owe on your house and what it's worth. So, when home prices are growing, equity is too. And with the recent spike in home prices, equity has surged. In fact, according to Black Knight's most recent Mortgage Monitor Report, tappable equity – the amount available for homeowners to borrow against while still retaining at least 20 percent equity in their homes – grew 37 percent over year-before levels during the second quarter of this year. Ben Graboske, Black Knight's president, says homeowners have made big gains. “This is by far the strongest growth we've ever seen and equates to some $173,000 in equity available to the average mortgage holder, a $20,000 increase in just three months,” Graboske said. According to the report, tappable equity hit a record high at the end of the first quarter, reaching $8.1 trillion. During the second quarter, it added an additional $1 trillion to that total.