- How many kWh the grid has to provide in exchange.
- How many kWh are obtained from other sources in order for this kWh to have been produced.
- How much CO₂ will be released for that kWh, considering the entire lifecycle of the source.
So that we can identify which other electricity production means would have been preferable (both in terms of total energy expenditure, and total CO₂ released).
At the moment, "net negative energy involved" seems like a proxy metric to me, and I don't know a proxy for what precisely.