Amazon Web Services LLC has launched a new auction room-style purchasing package for its EC2 cloud computing rental service.

The firm said in a statement today that customers could now use a new option called “Spot Instances” that allows them to bid on unused Amazon EC2 capacity and run those instances for as long as their tender exceeds the current spot price.

However, the spot price will fluctuate regularly as it will be determined by supply and demand.

AWS, which is an Amazon.com subsidiary, said the service was available for free to those customers who already use its On-Demand Instances and Reserved Instances options in EC2.

“Spot Instances are well-suited for applications that can have flexible start and stop times such as image and video conversion and rendering, data processing, financial modelling and analysis, web crawling and load testing,” said AWS.

"By being flexible on when their instances run, coupled with the ability to bid what they’re willing to pay for capacity, customers can significantly lower their Amazon EC2 costs.”

Spot Instances can also open the vault on large amounts of extra cloud capacity for apps that need to be delivered speedily, said the company. ®