In a report on business deployments of open source software, published in full late last week, the Commission said that in "almost all cases" savings would be made by switching from proprietary to open-source software.
The findings come in stark contrast to assertions from Microsoft that Linux savings are a myth.
The Commission's work is based on detailed analysis of open-source projects in six European Union countries.
"Our findings show that, in almost all cases, a transition toward open source (produces) savings in the long-term cost of ownership," said the report, which was written by academics at the United Nations University in Maastricht, Netherlands.
Microsoft has attempted to persuade IT professionals and businesses that Windows can be cheaper than Linux, though its Get the Facts campaign. Get The Facts cited examples where Microsoft's software had offered a cost advantage over open source software.
The EC report also issued encouragement for organizations considering the Open Office applications suite. "Open Office has all the functionalities that public offices need to create documents, spreadsheets and presentations," the report said. "Open Office is free and extremely stable." It added that people were as productive with Open Office as they were with proprietary software.
The report did list two notes of caution. First, it said, short term costs will be higher for organizations migrating, even partially, to open source, largely because of the initial cost of training. Second, some workers may feel undervalued if they are required to work with free software.
The EC, the executive arm of the European Union, has taken several strides towards encouraging the development of open-source software.
In October, it granted $3.88 million (3 million euros) toward a project, called SQO-OSS, to test the quality of open-source software. And just before that, the Commission extended its open-source Web portal, the Open Source Observatory and Repository, to develop interoperability between applications.
By Richard Thurston