Reliable power is essential for instruments used in deep wells, where batteries may be unsuitable for long-term operation. We redesigned the blade of a small downhole turbine generator using computer-based optimization and verified it with simulations and laboratory tests. The new design improved a key flow-performance measure by 26.9 %. At the highest tested flow rate, torque increased by 30.2 % and rotational speed by 27.1 %, showing more effective conversion of flowing liquid into useful power.