Though nudges are gaining attention as complements to traditional policies, evidence of the interplay between these two policy instruments is lacking. Here, we discuss and evaluate how combinations of traditional tools with different types of nudges may affect individuals’ energy consumption. Through an online experiment, we assess the impact of an energy policy mix which combines a traditional instrument (tax rebate) and a nudge (goal setting and feedback). We introduce an innovative incentive-compatible task: participants are asked to optimize their energy consumption on a virtual washing machine. We find that combining the traditional and the behavioral tools results in negative interactions. Specifically, providing an economic prize incentivizes participants to achieve their energy-saving target. However, this effect is reduced when the nudge is included: by increasing the amount of information provided, the nudge diverts participants’ cognitive resources from the economic incentive and reduces its impact. Our findings suggest caution when designing policies which entail a combination of traditional and behavioral interventions.