Nearly 11 million borrowers are underwater on their mortgages, owing more than their homes are worth, according to CoreLogic, and yet home equity lines of credit are suddenly on the rise again.During the housing boom of the last decade Americans withdrew over $1 trillion in home equity. They did it through cash-out refinances, home equity loans, and home equity lines of credit. The latter allowed them to use their homes like an ATM. They spent the money on cars, televisions, vacations and fancy home upgrades. It was seemingly endless equity, until suddenly that equity was gone.
"Home prices are definitely a factor" in the recent rise home equity lines of credit, said Brad Blackwell, an executive with Wells Fargo Home Mortgage. "As they increase, people have more available equity."
(Read More: New Housing Fears: Home Prices Are Rising Too.)
Blackwell also pointed to increased consumer confidence, meaning borrowers now feel better about their ability to repay these loans. Both factors fueled a 19 percent jump in originations of home equity lines of credit at the end of last year, according to Equifax. In 2008, as housing was crashing, home equity line originations dropped 55 percent.
"Nationally we've seen a 31 percent increase in HELOC's year-over-year," said a spokesperson fromJPMorgan Chase.
With home prices up 8 percent year-over-year in December, according to the latest reading from CoreLogic, homeowners are regaining home equity at a fast clip—1.4 million borrowers rose above water on their mortgages through the end of September. That number likely increased as price appreciation accelerated toward the end of the year.
Does this mean a return to the reckless equity withdrawals of the housing bubble? Likely not.
"I would guess that most of the current home equity line borrowing is quite prudent. We know that it is being very conservatively underwritten with plenty of equity," said Guy Cecala, editor of Inside Mortgage Finance.
(Read More: Housing Already Shows Signs of a New Bubble.)
While it is too early to say exactly what borrowers are spending this new cash on, anecdotal evidence shows borrowers are largely sinking the money back into their homes.
"We are seeing more responsible uses today, like home improvements, education expenses or other major expenses that would be a more responsible use of a customer's home equity," Blackwell said.
The average home equity line in October of 2012 was just below $90,000 compared to October 2006, when lines averaged just over $100,000, according to Equifax.
Despite the recent surge, volume is still down dramatically from the height of the housing boom. Borrowers in 2012 took out a collective $7.2 billion in home equity lines through last October, compared to just over $28 billion in 2006.
(Read More: Why Home Builders Won't Drop New Home Prices,)
The numbers are expected to go up in 2013, not just because home prices are rising, but because interest rates are rising. With higher rates, borrowers will not want to give up their rock-bottom fixed rates to do cash-out refinances; rather, they will turn to home equity lines instead. While these lines usually carry variable rates, banks are now offering new products with fixed rates. Wells Fargo recently promoted a line of credit where a portion of the loan is fixed for up to three years.
"We clearly want to lend, and we want to lend to the types of needs that our customers have," Blackwell added.
—By CNBC's Diana Olick; Follow her on Twitter @Diana_Olick or on Facebook at facebook.com/DianaOlickCNBC
