Providing sufficient dietary energy is the most expensive cost for a swine facility, and high barn throughput is now not always the way to gain the most net profit. Energy comes from starch, protein, fat, and fibre which are all used with a different efficiency. Current diets often use a wide variety of ingredients, and the price relationship between ingredients has changed, making the cost of formulating present diets more complex than in the past. Once obtained by the pig, energy can be used for maintenance, fat gain, or lean gain. Maintenance uses 25-35% of the energy intake: this will need to be accounted for if pigs are kept in the barn for a longer period of time. The trade-off for using a less expensive, lower energy diet is that the pig will be in the facility for longer, and maintenance and space costs will be higher than for a quicker throughput. When lowering dietary energy concentration it is important to consider the energy intake of the pig. At too low a concentration, the pig may not be able to consume enough feed to maintain the same growth rate as a higher concentration feed. The intake of feed varies among farms, and it would be best to create a farm-specific feed intake curve to determine what energy concentration will be best. Other aspects of the diet will have an impact on carcass characteristics as well, for example dietary fat. The source and the quantity of fat in the diet will affect the deposition and firmness of the carcass fat. Overall, dietary energy concentrations and sources should be carefully considered to lower costs, but the other aspects of the diet should not be overlooked.