Cutting the electricity cost of geographically distributed data centers is a hot topic in the area of cloud computer. Each of current workload dispatching mechanism only considers one factor that impacts the electricity cost of geographically distributed datacenters and thus cannot achieve the global minimization. This paper proposes a smart workload dispatching mechanism, Joint Electricity Price-aware, Cooling Efficiency-aware, and Dynamic Frequency Scaling-aware Datacenter Load Balancing(JECF), to cut the electricity cost of distributed Internet datacenters. JECF jointly considers the time-variant electricity prices among datacenters, the efficiency of the cooling system, and the dynamic frequency of active servers in each datacenter, and thus, reduces the total electricity cost of distributed datacenters by trading off the electricity cost consumed by active servers and cooling systems. The evaluation results show JECF outperforms existing datacenter workload dispatching mechanism and achieves significant reduction on the electricity cost of distributed Internet datacenters.