A thorough study assessing the exposure contributions from Zigbee smart meter devices operating at 868 MHz, revealing lower or similar levels to those at 2.4 GHz and well below ICNIRP general public reference levels.
Introduction to Zigbee Smart Meter Radiation Study
The study aimed to evaluate the exposure to radiofrequency electromagnetic fields from smart utility meters operating at 868 MHz under laboratory-controlled conditions. The maximum 6-min averaged exposure recorded was 0.1 mWm-2, which is less than 0.0024% of the corresponding 1998 ICNIRP general public reference level. The measured duty factors were less than 2.8%. The study found that the exposure contribution from Zigbee smart meter devices operating at 868 MHz is generally lower than, if not similar to, those operating at 2.4 GHz.
Background on Smart Meters and Zigbee Communications
Smart meters provide utility companies with energy consumption data and help consumers understand and optimize their energy use. In the UK, HAN transmissions use Zigbee, a communication protocol that uses low-power radiofrequency (RF) electromagnetic fields (EMF) signals. Smart meter HAN communications operate at a frequency of 2.4 GHz in approximately 70% of GB premises, but an additional HAN solution using 868 MHz is specified for premises where the 2.4 GHz solution does not work due to signal path loss and attenuation (in approximately 25% of premises).
Study Methodology and Measurements
The study involved measuring power density and duty factor values around smart utility meters in an anechoic chamber. The transmission periodicity of the devices is roughly every 15 seconds, except for the gas meter (GM), which is usually configured to transmit every 30 minutes. The power density measurements were made in the active Zigbee channel at distances of 0.6 and 1.1 meters from the front of each of the smart meter devices.
Study Results and Comparisons
The study assessed nine smart meter devices (three CHs, three IHDs, and three GMs) operating at 868 MHz. The maximum 6-min average RMS power density was 0.10 mWm−2, 0.002% of the ICNIRP general public reference level (4.34 Wm−2 at 868 MHz, for 6-min RMS average). The maximum peak power density value at 868 MHz was 3.9 mWm−2, which is less than 0.0001% of the ICNIRP GP reference level (4340 Wm−2, for burst peaks).
The study found that the maximum duty factors from smart meter devices operating at 868 MHz were higher than that of smart meter devices operating at 2.4 GHz (1.2% maximum across 56 devices). However, this is still much lower than the duty factor reported for a WLAN Access Point, with a value of 12% and average of 5%.
Comparison with Cell Phone Radiation
In comparison to cell phone radiation, smart meters emit significantly lower levels of radiofrequency electromagnetic fields. Cell phones have a higher power output, ranging from 0.2 to 2 W, and are typically used in closer proximity to the body. This results in higher exposure levels for cell phone users. The Specific Absorption Rate (SAR) is used to measure the rate of radiofrequency energy absorbed by the body from a cell phone, with regulatory limits typically set at 1.6 W/kg in the United States and 2 W/kg in Europe.
In contrast, the maximum 6-min average RMS power density found for smart meter devices operating at 868 MHz in this study was 0.10 mWm−2, which is 0.002% of the ICNIRP general public reference level. Moreover, smart meters are installed at a fixed location, usually on an exterior wall or in a utility room, and are not in constant close contact with the human body, resulting in lower exposure levels.
It is also worth noting that while cell phone usage patterns may vary, some individuals may use their cell phones for extended periods during the day, leading to a higher cumulative exposure to radiofrequency electromagnetic fields. Smart meters, on the other hand, transmit data at regular intervals (approximately every 15 seconds for electric meters and every 30 minutes for gas meters), resulting in a much lower duty factor and overall exposure.
The exposure contributions from 868 MHz smart meter devices were found to be generally lower than, if not similar to, that from 2.4 GHz smart meter devices, and at least four orders of magnitude lower than the 1998 ICNIRP GP reference level, at 0.6 m distance.
Comparison with Cell Tower Radiation
In comparison to cell tower radiation, smart meter devices emit significantly less radiofrequency electromagnetic fields. Cell towers typically emit power densities ranging from 0.1 to 1 mWm−2, which is much higher than the 0.10 mWm−2 maximum 6-min average RMS power density found for smart meter devices operating at 868 MHz in this study. Moreover, cell towers are known to have a duty factor of up to 100%, whereas smart meter devices in this study had a maximum duty factor of 2.8%.
Top 10 FAQs on Smart Meter Radiation
- What is a smart meter, and how does it work?
A smart meter is an electronic device that records energy consumption data and communicates it to utility companies for billing and monitoring purposes. It helps consumers understand and optimize their energy use through regular and accurate readings. Smart meters use a communication protocol called Zigbee, which employs low-power radiofrequency electromagnetic fields (EMF) signals for data transmission.
- Are smart meters safe in terms of radiation exposure?
Yes, according to the study conducted on Zigbee smart meter devices operating at 868 MHz, the exposure levels are well below the ICNIRP general public reference levels, making them safe in terms of radiation exposure.
- How does the radiation from smart meters compare to Wi-Fi routers and cell towers?
The radiation from smart meters is significantly lower than that of Wi-Fi routers and cell towers. Smart meters emit a maximum 6-min average RMS power density of 0.10 mWm−2, whereas Wi-Fi routers have an average duty factor of 5% and cell towers emit power densities ranging from 0.1 to 1 mWm−2.
- How often do smart meters transmit data?
Smart meter devices typically transmit data every 15 seconds, except for gas meters, which are usually configured to transmit every 30 minutes.
- What is the duty factor, and why is it relevant?
The duty factor is the ratio of the active transmission time to the total observation time. It is relevant because it helps determine the average power density and overall exposure to radiofrequency electromagnetic fields.
- What are the ICNIRP general public reference levels?
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has established guidelines to limit exposure to radiofrequency electromagnetic fields. The ICNIRP general public reference levels are designed to protect the general public from potential health risks associated with radiofrequency radiation.
- What is Zigbee?
Zigbee is a communication protocol that uses low-power radiofrequency (RF) electromagnetic fields (EMF) signals for data transmission. It is commonly used in smart meter HAN (Home Area Network) communications.
- Are smart meters mandatory?
Smart meter installations vary by region and utility company. In many countries, smart meters are being rolled out as part of government-led initiatives to improve energy efficiency and reduce consumption. However, in some cases, customers can choose to opt-out.
- How can I minimize my exposure to smart meter radiation?
Although the radiation exposure from smart meters is minimal and well below safety limits, you can minimize exposure by maintaining a safe distance from the meter and avoiding prolonged close contact with the device.
- Can I request a smart meter that operates at a lower frequency?
Smart meter frequencies are generally determined by the utility company and regulatory standards. In the UK, most smart meters operate at 2.4 GHz, but an additional HAN solution using 868 MHz is specified for premises where the 2.4 GHz solution does not work due to signal path loss and attenuation. However, the study found that exposure levels for both frequencies are well below safety limits.
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Evaluation of Exposure to Radiofrequency Electromagnetic Fields from Smart Utility Meters operating at 868 MHz
Conflicts of interest: The author declares that there are no conflicts of interest.