Why is the inverter reading different from the meter reading?
- Inverter Reading Greater than Meter Reading
In most instances, the inverter displays a higher power output compared to the meter reading. This difference arises due to several factors:
Transmission Losses: The power generated by the inverter is transmitted to the meter through an AC cable. During this transmission, some power is lost due to the resistance of the cable. The extent of this loss depends on various factors including the material of the cable (copper or aluminum), its length, and the wire diameter.
Inherent Measurement Differences: The inverter measures the output power directly, while the meter measures the power that reaches your home after transmission losses. Thus, the reading on the inverter is generally higher as it does not account for these losses.
- Inverter Reading Smaller than Meter Reading
Although less common, there are cases where the solar power inverter’s reading is smaller than the meter’s reading. This can be attributed to the following reasons:
Measurement Accuracy: Both inverters and meters have inherent measurement inaccuracies. The accuracy of an inverter’s current sensor is typically around ±0.5%. On the other hand, electricity meters have different accuracy classes such as 0.2s, 0.5s, and 1.0s, indicating an error margin of ±0.2%, ±0.5%, and ±1.0% respectively. Household electricity meters usually fall into the 1.0s class.
Error Overlap: If the inverter’s sensor has a positive error (overestimates the power) and the meter has a negative error (underestimates the power), the readings can be closer than expected, or in some cases, the meter might display a higher value if the transmission loss is minimal.