At Twente University, researchers have taken up validation of smart meter readings.
Turns out that smart meters tend to measure undimmed (unreduced) energy consumption for devices that can be dimmed with pulse width modulation or are otherwise deforming perfect sine waveforms of AC. That’s often the case then CFL or LED lights are being dimmed. Also, households with solar panels or electric car chargers can be affected.
The error is up to factor 6 (580%).