Precision agriculture (PA) technology provides a means to increase equipment productivity and field efficiency, and input efficiency; however, the potential of PA technologies to enable smaller, autonomous machines has yet not been realized in the market place. In developed countries, the size of tractors and implements continue to increase. Such trend cannot continue indefinitely because of size, technical and cost constraints. A long operating life for agricultural equipment enables a greater benefit relative to the high initial cost and investment. However, long equipment life can lead to technologically obsolete machines with potential incompatibility and sub-optimality, since machinery and PA technology should evolve together and be used as a package. Similarly, power system technologies with potential application in agricultural machines are also evolving quickly and issues of renewability and sustainability are becoming common priorities, with demands for standardization and certification. The concept of small modular and scalable intelligent machines tries to address the challenge of gaining higher productivity with reduced costs and power. In particular, in this paper different weeding technologies were compared using performance metrics including work rate and energy density. Conventional processes, using common tractors were compared with robotic weeder designs to evaluate performance, size and energy requirements. Forecasts of possible future trends of agricultural machine size, PA technology integration and power system technology deployment were derived from this work.