Understanding energy consumption is more important now than ever, and the tools of the smart home provide some interesting possibilities for energy monitoring. This article shows how to use an energy consumption meter to answer practical questions about the power usage of home appliances.

A consumption meter is a device that sits between the appliance and the socket outlet. Some versions include a graphic display to show the current power consumption and the total consumption. Other models support some form of networking to transmit data to a hub or computer system for viewing and further processing. I'll look at two consumption meters that transmit wireless data output. The Voltcraft SEM6000 uses the low-energy Bluetooth variant known as Bluetooth LE to transmit the data, and the Delock 11827 supports WiFi (Figure 1). A Raspberry Pi acts as the data logger, recording the measured values over several days. Simple Python scripts handle the task of evaluating the profiles. This article was written for the 230-volt European electrical environment, but alternative consumption meters are available for the 120-volt North American market, and, with a little ingenuity, you can adapt these techniques to address other energy consumption questions in other settings.

Getting a Reading

Active current and active power are proportional to each other, which means you only need to record the active power and the time of measurement. Emitted interference from the mains current and the tiny antennas limit the radio range of the devices in Figure 1 to a few meters. The Voltcraft measuring connector therefore expects to find a computer nearby with which it can pair. Delock's version tries to log onto an existing WiFi network. If the signal at the measurement location is too weak, you can use a mobile router to log the computer and measuring device onto its WiFi network.

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