Gold open access, which is often wrongly named as “author-pay model”, is mostly relying on journals that are financed or published by higher education and research institutions. According to the DOAJ (Directory of Open Access Journals), 67% of existing open access journals don’t ask for a publication fee from article authors. The remaining third relies on the payment by the author – or more likely his institution – of an Article Processing Charge (APC) in order to finance the open distribution of accepted papers. Another source of APC are the traditional journals available on a subscription basis but which also propose an open access option on the article-level: this model is referred to as “hybrid open access”. The monitoring of APC costs has started to gain interest at the end of the 2000’s and became an important data in some countries (United Kingdom) after 2012. APC expenditures are now considered as an important stake at the european level. After a presentation of the current situation in Europe regarding APC monitoring, the study focuses on three different methods that can be used in HER institutions in order to get a better knowledge of this source of expenditure: large bibliographic database, publishers requests and accounting system. These methods have been applied to two HER institutions (Aix-Marseille Université and Université de Lorraine) on a 2 to 3 years timespan (2013-2015). The article presents some first results that help to identify and discuss the strenghts and weaknesses of each of the three methodologies.