Take a look at the stuff made with rice protein, they usually have fewer fillers. All protein powders with have 4 x grams protein of calories. Most all food companies use the formula (4 x g of protein) + (4 x g carbohydrates) + (9 x g of fat) = total calories. The extra in some protein powders is due to the fillers and binders or flavors.
take a look at trueprotein.com, you can custom blend your protein, or look at their pre-mixed solutions. they have some low calorie blends as well. I personally like the pre-mixed dc blend, the premium flavors taste the best and they mix very well.