Digitizing analog meters into the IoT where meters can be read remotely is a solution which is both environmentally and economically beneficial. This study investigate show energy critical systems can gain a longer lifespan by optimizing their energy consumption. The purpose of this study is to evaluate the energy consumption of energy critical systems with different wireless data transfer protocols. This is conducted with experiments and observations.The data was collected by setting up two testbeds where the wireless transmission interfaces WiFi and BLE were used to send data between two microcomputers. These testbeds measured the energy consumption when altering with the variables of the two transmission protocols.The result shows that the internal protocols of WiFi were greatly affected by the changes made in the variables compared to BLE during the experiments. The results also show that when calibrating the different variables, the energy consumption is reduced by up around 52%. Furthermore, the result indicates that there is energy to saveif you optimize transmission power to a specific environment.In this study, BLE has little to no change to the energy consumption when changing the different variables. When investigating the internal protocols of WiFi, they are greatly affected by the different variables being changed. A lower transmission power can be more energy efficient but at the cost of shorter range and eventually a higher packet loss.