In smartphones these days, according to J.D. Power and Associates, nothing matters more in terms of customer satisfaction and loyalty that how fast the battery drains.

“Both carriers and manufacturers recognize the fact that battery life needs to be improved,” said J.D. Power’s Kirk Parsons in a press release issued Thursday. “However, the study uncovers the need for a greater sense of urgency — short battery life can result in perceived phone problems, higher rates of merchandise returns and customer defections.”

Apple (AAPL) has traditionally placed a premium on the iPhone’s battery life — holding off on features (like support for Flash) and new networking technologies to conserve power.

That bet seems to be paying off. The iPhone finished first in J.D. Power’s smartphone survey the seventh time in a row, with a score of 839 out of 1,000.

HTC was No. 2 at 798, and Samsung No. 3 at 769, below the industry average.