New strategies to enhance heating and cooling systems efficiency are investigated nowadays. The parallel running variable speed pumps in closed loop system are studied to optimize the system for lower energy consumption. This study handles a closed loop system that consists of variable speed circulation pumps. The experimental results show that about 70% of pump energy could be saved by using this optimal control strategy when compared to traditional control methods. The tests were conducted under the same hydraulic conditions for similar pumps in parallel running condition. The overall best energy efficiency is achieved with the same speed ratio for circulation pumps.