The energy requirement is a key criterion for the selection and use of a grinding process. Ultrasonic dispersion is extensively used to disperse submicron agglomerated powders in liquid suspensions. Suspensions of silica agglomerates were ground with solids concentration up to 50% by weight. The fragmentation or grinding rate is inversely proportional to suspension volume. Starting from a semiempirical expression that relates fragmentation rate to particle size, suspension volume and ultrasonic power, energy consumption laws for both eroding and non-eroding powders are developed. Experimental results supporting the energy consumption laws are given. Lower power input for ultrasonication favors efficient energy use. For eroding powders (e.g. silica, zirconia) the energy expenditure per unit powder mass (specific energy) by ultrasonic grinding is lower than that of conventional grinding techniques. In contrast, it is slightly higher than ball milling for non-eroding powders (e.g. titania).