Resales of year-old iPhones start heating up

More customers are upgrading to the latest Apple smartphone every year, creating a bigger market for the previous year's models.

Apple's iPhone 6, even used ones, should continue to be a big draw for customers. CNET

Want a year-old Apple iPhone on the cheap? Your chances of snagging one are now better than ever.

More customers are moving to upgrade their smartphones more quickly, as US wireless carriers transition away from the two-year contract. That's creating a much bigger resale market for used iPhones that are just a year old, according to data shared with CNET from both eBay and Gazelle.

"I think we're seeing an underlying trend that upgrade cycles are accelerating," said Sarah Welch, chief marketing office for Gazelle, a retailer specializing in electronics trade-ins. "There's much more variation now with how people purchase or lease their phones."

eBay's data shows a big shift in year-old resales on its site from 2013 to 2015. eBay

Early upgrade programs from the major US carriers are encouraging this change in consumer behavior, with more people looking to move up to the latest models every year. Apple is also getting into the mix, unveiling this month the new iPhone Upgrade Program that lets users bump up to a new smartphone every year.

These annual upgraders could benefit customers who are just as happy with used year-old iPhones. On eBay, Amazon, Gazelle, Glyde and other resale sites, used year-old models of the iPhone 6 cost roughly $300 to $500, depending on the model. A new iPhone 6 starts at $550 without a contract.

The consumer shift toward speedier upgrades over the past two years could help Apple keep up demand for its latest phones. The iPhone now makes up two-thirds of the company's revenue, so maintaining interest for the devices is critical for the Cupertino, California, company.

On eBay, year-old models accounted for 43 percent of US iPhone sales during the first half of September 2013, the time of year a new iPhone is usually announced. That figure rose to 50 percent in 2014 and 52 percent this year. Gazelle experienced a similar bump, with year-old trade-ins on its site rising from 28 percent during the same time in 2013 to 42 percent this year.

These statistics, however, don't mean most people now upgrade every year. In fact, a whole other set of customers now appear to be holding onto their phones for longer, or buying used phones, as the motivation for them to upgrade every two years dies off, Welch said.

So when is the best time to buy or sell a used model?

Representatives from both eBay and Gazelle said that on their sites prices for year-old models face their steepest decline a few weeks before a new iPhone is announced. So, sellers should be warned of that big drop, even if many of them can't avoid it.

For buyers, the most listings tend to hit eBay the days immediately after a new iPhone goes on sale publicly, which occurred Friday with the iPhone 6S and 6S Plus .

"We'll see tens of thousands of listings starting to add to our site on a daily basis," said Hal Lawton, eBay's senior vice president of North America.

That means the best selection and pricing for older models on the marketplace will likely be from Monday to Wednesday, said Vincent Payen, eBay's head of consumer selling.

So far, though, the resale market isn't offering many clues on how successful the new iPhone 6S will be. Still, the off-cycle "S" year, in which Apple adds some features but waits to do a major overhaul the year later, is expected to encourage fewer resales, Payen said.

"Last year, we saw massive, massive activity like we have never seen before," Payen said. "This year, it's too early to call."