I recently installed the Shelly Pro 3EM in my home to monitor power consumption, and it’s been quite an enlightening experience! While the active power (W) readings seem reasonable, I’ve been puzzling over the relationship between apparent power (VA), power factor (PF), and how they interact, especially during low loads.
For those unfamiliar, apparent power is calculated as voltage multiplied by current (U * I), and active power should theoretically be apparent power multiplied by the power factor (PF). However, in practice, there are discrepancies, particularly when the load is minimal. For instance, if a device on Phase C shows 88.8W but the calculation based on 146.9VA * PF (0.72) suggests it should be 105.8W, it raises questions about which value is more accurate.
I’ve been running firmware version 0.14.1 and observing this behavior both locally and through the web interface. While higher loads seem to align better, the lower end of the spectrum introduces noticeable errors. This has me wondering: is this a rounding issue, a miscalculation, or something else entirely?
I’d love to hear from others who might have encountered similar phenomena or have insights into how these values are computed and displayed. Are there specific conditions or configurations that influence these discrepancies? It’s fascinating to dig into the technicalities, but I’m also eager to ensure my setup is providing reliable data for energy monitoring.
If anyone has tips or experiences to share, especially regarding optimizing power factor or interpreting these metrics more accurately, I’d be grateful for your insights! Let’s continue exploring the nuances of power consumption together. 