Heat production (HP; indirect calorimetry) of six Large White castrated sows (mean BW 208 kg) kept individually in metabolism cages at 24°C and fed once a day (d) at about maintenance energy level (415 kJ ME/kg BW 0.75) and their physical activity (standing versus lying) were recorded continuously over 24 h after a meal. Each measurement lasted 5 consecutive days and was repeated 8–10 times for each sow over 9 months. HP related to activity (AHP) was calculated according to a statistical model in which HP was a function of time after the meal and standing activity. Resting heat production (RHP) corresponded to the difference between HP and AHP. HP and AHP averaged 402 kJ kg BW −0.75 d −1 and 14.9 kJ/min (or 0.26 kJ kg BW −0.75 min −1), respectively. Mean duration of daily activity was 241 min. AHP was then equivalent to 62 kJ kg BW −0.75 d −1 or 15% of HP. Consequently, RHP averaged 340 kJ kg BW −0.75 d −1. Minimum RHP (23 h after the meal) was 290 kg BW −0.75 d −1. These values were significantly different between sows. Meal duration averaged 14 min. Variations in activity, total HP and RHP over the day are presented. The mean increment of HP related to food intake represented about 15% of ME supply. Compared to other species, the energy requirement for standing activity in pigs is distinctly higher.