Specific water cost for large scale BOT seawater desalination plants have reached today (May 2001) a level in the range of US$0.8-1.0/m(3). This is well below the level of approx. US$3.0-4.0/m(3) only 15 years ago. The decline in cost is due to continuous technological improvements in both membrane and thermal systems. In spite of the cost level reached today further cost reductions are required. A potential area for fin-ther cost reduction are the pumping systems especially the speed control of pumps. Speed controlled brine recycle pumps for MSF-plants have been utilized already in the past in some cases however they are not yet state of the art for RO-plants and MED-plants. Speed control of pumps offers various advantages, i.e. easy fully automatic start-up, easy shut-down, reduced energy consumption as the pump can be operated always at its optimal point without important throttling losses in pressure and/or flow control valves, longer lifetime of membranes in the case of reverse osmosis due to reduced compaction etc. The paper describes for RO, MSF and MED plants the technical arrangement possibilities for speed control systems for small and large pumps and compares the energy consumption with conventional arrangements. It will be demonstrated that for RO high pressure pumps speed control results always into an overall cost saving and for thermal desalination plants (MED, MSF) in many cases.