Retrofitting energy meters with LoRa

The global energy crisis, which began with the war in Ukraine, has led to an increase in energy prices. Due to the rising costs, real estate owners, homeowners and tenants are much more conscious of their energy use and have an increased need for visibility to be in control of their bills and their environmental impact.

Furthermore, there is a compelling legislative momentum driving the adoption of smart meters. For instance, by the end of 2027, Swiss utility companies are mandated to replace at least 80% of traditional electricity meters with smart meter systems. Similarly, Germany recently passed legislation mandating smart meter installation for most consumers by 2030.

Utilities are therefore rolling out smart meters, but their traditional use case is primarily to provide simple billing information. This requires very limited data (typically replacing an annual visit). For local data owners, there are different customer interfaces available, such as Modbus, ZVEI, and pulse. While Modbus and ZVEI require the cooperation of the utility company to provide the interface (they are legally obliged to but not always highly motivated), pulse metering offers an easy way to access short interval meter data. 

In this article, we will look at how energy meters can be retrofitted with LoRa pulse sensors to enable remote metering of energy consumption.

How do pulse energy meters work?

Energy meters installed in buildings typically contain a component that produces pulses for each unit of energy, water, or gas consumed at any moment. Taking the example of an electricity meter, when a user turns on a lamp or uses a hairdryer, the pulse generator circuit inside the meter will detect the passing current and generate a pulse signal. Each pulse corresponds to a specific amount of energy consumption (typically 1 Wh or 1/1000th kWh). The meter counter captures this signal, increments the count, and derivates the energy consumption.

Energy meters produce pulse outputs in different ways. Most often, the pulse output is given by a switching relay. The issue with many electricity meters is that pulse output connections are not available or not made accessible by the utility company. However, most modern counters have an optical pulse output LED. This is precisely what we can use to measure energy consumption with an optical sensor equipped with LoRa transmission.

In this situation, the optical sensor is placed on the energy meter and reads the light pulse emitted by the LED. It then transmits the count to the application server via the LoRaWAN network. Counting pulses will inform how much energy is used, while the time between the pulses indicates the immediate power draw.

Optical pulse counting

As discussed above, the electricity consumption is measured by counting the pulses, each representing a unit of energy consumed. 

It is important to note that different energy meters will have different ways to generate these pulses. Most notably, one has to take into account the pulse multiplier of each equipment (available in the datasheet of your energy meter). For example, if a meter has a multiplier of 10 pulses per kWh and records 50 pulses in one hour, the resulting energy consumption will be calculated as: 

Ensuring that the right pulse multiplier is used to derive the energy consumption is essential.

Secondly, the “shape” of these optical pulses must be taken into account, and a suitable optical sensor must be chosen as a result. Typically, you want to ensure that the sensor can detect the smallest pulse width and intensity.

LoRa devices for optical pulse metering

As different energy meters have different characteristics, there is no one-size-fits-all when choosing an optical pulse meter sensor. Make sure to read the datasheet of your energy meter properly, understand how the pulses are generated, and pick an optical sensor accordingly.  Additionally, review the sensor's datasheet to ensure it is fully compatible with your energy meter, with no limitations.

Two devices that were tested successfully at akenza are the Flash’O from Watteco and the Senlab M from Sensing Labs. These two devices can be connected to the akenza platform easily thanks to our Device Type Library, containing payload decoders for more than 200 devices.

To accommodate the different pulse multipliers mentioned above, we typically use a custom field in the Device Type (a.k.a. payload decoder) to derive the conversion to kWh and compute the resulting energy consumption.

Visualizing the energy consumption

The akenza payload decoder directly delivers the total pulse count with each received message, the increment between two messages, and the resulting consumption. The live data and historical data can be visualized directly in the device data overview (see below). Stateful device types enable to deliver the pulse count increment and other metrics calculated based on successive messages directly from the payload decoder. 

In addition to that, the Dashboard Builder of akenza can be used to create a custom overview of the energy consumption to be shared with interested stakeholders.

The collected data can also be transmitted to third-party tools to be further analyzed, for example, for ESG reporting. Various output connectors are available for this.

Limitations

As we are using an external device to measure light pulses, some situations deliver better results than others. Moreover, if you have equipment that handles energy consumption and production over the same circuitry, a pulse would be generated in both cases. Counting only the pulses linked to energy consumption becomes less easy.

For better results and for users who need more complete information, using a data interface (e.g., MBUS, HAN) instead of the LoRa optical sensor is recommended. We will cover this in a future article.