Brittany Sowacke | Bloomberg | Getty Images  Workers connect drill bits and drill collars, used to extract natural petroleum, on Endeavor Energy Resources LP's Big Dog Drilling Rig 22 in the Permian basin outside of Midland, Texas.  And demand for oil is still growing, though more slowly, said Fadel Gheit, Oppenheimer & Co.'s senior energy analyst. "There will be more people using more energy," he said, "but more efficiently."  "Saudi Arabia is playing hardball and has huge cash reserves to ride out lower oil prices," Gheit said. "It's drawing a line in the sand." But oil stocks, which tend to be overbought or oversold, are still good investments long-term, he said.  Read MoreWhere to find the dividend stock kings of 2015  With a hefty discount to the price-to-earnings ratio of the S&P 500, energy stocks look enticing. Consider this factoid from S&P Capital IQ: There have been six times since 1990 that the S&P 500 Energy Index traded at or below its current "relative strength" reading. Over a 24-month time frame, the S&P 500 Energy Index was positive six of those six times and beat the S&P 500 five of six times. It also outpaced the S&P 500 by an average 16.2 percentage points. In comparison to the last nine historical oil price shocks, there have only been two times when energy has been cheaper on a relative basis when oil prices troughed: in the wake of 9/11 and in late 2006.  Some market pundits think energy is set up to be a classic value trap, but some financial advisors say that it's time to tiptoe back into energy using ETFs, especially for investors with a patient, long-term outlook.  "I'd be adding energy ETFs right now," said Joseph Tatusko, chief investment officer at Westport Resources Management in Connecticut. Since no one knows when oil prices will hit their bottom, Tatusko also recommends using dollar cost averaging, which helps lessen risk. Dollar cost averaging is buying a fixed amount of a stock, or fund, on a fixed schedule so you don't invest too much at any one time in what can be a volatile market.
The energy sector is worth a look even for investors wary of a short-term rebound trade—and ETFs may be the way to tiptoe back in.