Limited fossil fuel resources along with the ever-increasing demand for inexpensive and environmentally friendly energy are the driving factors of geothermal and waste heat recovery technologies. In the last two decades, the Organic Rankine Cycle (ORC), has been improved and modified to better adapt the cycle to the various conditions of heat sources and has become a preferred means of exploiting low potential heat resources of various types and been widely used in many applications as an efficient and reliable energy source. This paper represents results for the 250kW power unit, which utilizes the R-245fa refrigerant for ORC cycle in low temperature range up to 150 deg. C. The detailed design process of an ORC turbine is presented and discussed. The effect of general turbine configurations and component design on turbine efficiency and structural integrity is studied. Cost and weight cut off aspects of turbine construction also discussed. The level of efficiency achieved as a result of turbine optimization, is at the top for this class of small turbines. Final variant represents one stage axial turbine with integrally bladed disk, inlet scroll and outlet tail pipe. Structural optimization has been performed to minimize rotor weight at an acceptable level of stress and frequency safety factors.