We present a case study for a price-taking hydropower producer trading in the three short-term energy markets, day-ahead, intra-day and the balancing market. The study uses a scheduling software with a detailed representation of a real Norwegian power plant optimizing the operations and trade for historical market data from 2015. The motivation for the study is to make an assessment of the value of trading in multiple markets relative to day-ahead trading only, utilizing a simplifying perfect foresight assumption. This gives the basis for assessing the value of developing more complex models with a more precise representation of uncertainty in the decision process. The analysis show a significant added value from participating in more markets than day-ahead, with the balancing market giving the largest contribution.