Mine is a Transformerless inverter which supports data collection via a USB stick.
The data is uploaded to Fronius solar access software and I manually add the data to pvoutput.
Yes when I heard some of you were doing it I wondered if I could too. Mine are a free set up and a modem on the meter sends the info to Head Office, I don't know if the inverter has any cards in it to allow me to access it.
I believe a Current Cost EnviR meter with NetSmart bridge can upload data every 5 minutes or so to PVOutput without the need to have your PC switched on. Both generation and consumption data can be logged with the right equipment.