King penguins Aptenodytes patagonicus are known to change their diving behaviour in response to changes in both prey location and their breeding status through the early stages of the breeding cycle (austral summer and autumn). However, little information exists on whether and how these changes affect the energy expenditure of such behaviour. By deploying heart rate and hydrostatic pressure data loggers, we investigated detailed changes in the dive time budgeting of king penguins during foraging dives across the breeding season, in the same individuals, and the associated changes in estimated oxygen consumption during those dives. Maximum dive depth, duration, bottom duration, feeding events (indicated by wiggles) per dive and post-dive duration increased through the study period. While a foraging dive later in the breeding season was energetically more costly than a dive earlier in the season, the overall rate of energy expenditure did not change, nor did energy cost per unit prey capture. These findings indicate an ability of king penguins to adjust their foraging dive behaviours through the summer and autumn without affecting the energetic costs of diving to capture prey. Such plasticity may be necessary to compensate for changes both in prey location and abundance, and in the energy requirements of the chick over time.