Purpose of review Indirect calorimetry is increasingly recommended to guide energy delivery in the ICU. This review aims to provide a critical overview of current literature in support of these recommendations. Recent findings There is insufficient evidence to ascertain a mortality benefit from indirect calorimetry-guided energy delivery. However, large variations in energy expenditure during critical illness pose a risk for significant under- and overfeeding if indirect calorimetry is not routinely used. Summary Even in the absence of demonstrable clinical benefits, there is a strong physiological rationale in favor of performing indirect calorimetry. Measurements can be prioritized in complex patients and should be repeated during prolonged ICU stay.