Recommended by What's your old iPhone worth?

Next week, Tim Cook will stand on a stage in San Francisco and unveil a new iPhone model.

Shortly after the Apple chief executive delivers his speech, some of you will start wondering about upgrading your current iPhone.

But what is it worth, and what can you expect to pay second hand iPhone for older iPhones?

Figures from Trade Me show there is a spike in searches for iPhones after each new model is released.

However, data from January to June this year shows that while about 100,000 iPhones were listed on the site it's not always the latest models that get the most attention.

The results show the iPhone 5 was most popular handset in terms of the number of listings created during that period.

This was followed by the iPhone 5s (2013), the iPhone 4s (2011), then the iPhone 6 (2014) in 4th place.

The most purchased iPhone over the six-month period was the iPhone 5 followed closely by the iPhone 5s, and the iPhone 4s. In 4th place again was the iPhone 6.

The demand for smaller, more affordable iPhones possibly shows Apple made a smart move by released the 4-inch iPhone 5se earlier this year.

However, people still covet the latest phones, with data showing the 6 model is the most popular when it comes to searches.