Abstract This paper presents an application of term frequency (TF) as a means of identifying useful trends from text documents. Of particular interest is the relationship between publication patterns, as characterized by TF, and the underlying technological developments. To demonstrate the usefulness of our approach, a case study on distributed generation (DG) was conducted. Important sub-domains of DG research were identified and the associated TF values were extracted using relevant keywords. The evolution of these values through time helps to highlight key trends in the development of DG-related technologies.