Sun Microsystems is expanding its utility computing service from the US to 23 countries in Asia and Europe, including the UK.

Utility computing, in which customers pay an hourly rate for access to a Sun data centre, began as a US-only pilot in March but is now ready for a large geographic expansion, said Rohit Valia, group product manager for the Sun Grid Compute Utility.

Sun charges $1 per CPU per hour to access a network of Sun x64 hardware running the Solaris 10 operating system. End users can now access the utility from Australia, Austria, Belgium, Canada, China, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, India, Ireland, Italy, Japan, New Zealand, Poland, Portugal, Singapore, Spain, Sweden and the UK.

IBM, Hewlett-Packard and other vendors provide similar utility services, also called on-demand computing or, more informally, computing "in the cloud." The services are for organisations that have a short-term need for extra computing capacity but don't want to pay out to add to their own data centres. They only have to build out their own capacity for an average level of usage, not the occasional spike, said Valia.

"Our business model is around charging for CPU cycles, not idle CPUs. We only charge when your CPU is actually processing data," he said.

Sun is also adding a feature called Internet Access so that Sun customers can interact, through Sun's utility data centre to the internet, with other companies that have resources the customer might want to use for a particular project. And Sun is also offering a limited beta programme for developers called Job Management Application Programming Interfaces, which allows users to perform production scale tests to build software applications using