To improve the efficiency of electricity distribution, smart grids allow communication between their devices. Pieces of legacy equipment operating in the distribution network do not communicate using any commercial protocol, such as DNP3, IEC 61850, or Modbus. Thus, herein, a middleware is proposed to allow the integration of the legacy electrical equipment into a smart grid using wireless sensor networks (WSNs). Each piece of legacy electrical equipment is connected to a sensor node, and the WSN sink node runs a middleware to enable the integration of this device with a smart grid, according to the commercial communication protocols. The mid- dleware model is proposed to guide users in the development of a WSN-based system for integrating electrical equipment into a smart grid. The middleware was validated in a real environment, which is related to the concept of power metering. Experiments were performed using the software supervisory control and data acquisition and distributed test manager to validate the communication between the electrical equipment and the computer of the power substation control centre.