We recommend that you leave a football's worth of space at the top of the washer and fill up the dryer no more than 1/3 of the way. Many of our customers fill up the dryer to the brim in an attempt to save money, but their laundry takes much longer to dry, so they really aren't saving money because they need to add extra time. If you overfill the washer, the laundry will not be able to come out of the water and splash back down. It just spins around the drum, not getting the proper agitation to get clean.
By properly filling the machines, you will get the most bang for your buck AND get the best clean possible.