Calorie Comparisons. If you make canned condensed potato soup with milk, each cup has 149 calories. Use water instead, and you'll reduce the calories to 73 per cup. Potato soup from a restaurant has around 190 to 210 calories per serving. Potato soup made from scratch at home can vary greatly in calories depending on the recipe you choose. A recipe made with bacon and slightly less than 1/2 cup of cheddar cheese per cup of soup has 430 calories per cup.