In this article, we discuss energy consumption of producing firms on aggregate production planning. While almost constant energy consumption can be the case for a producing firm, highly fluctuating energy demand can occur as well. Together with volatile energy supply, e.g. due to renewable energy sources, this combination of fluctuating energy supply and demand can result in planning uncertainty and high energy costs. We propose different case studies in which such high deviation in the electricity consumption of a producing firm occurs due to aggregate production planning without appropriate consideration of energy consumption.