[kingstnap]

Being a first-party source and reliability are orthogonal concepts. But yes, he doesn't need to bring receipts; he is the receipt.

He can take the number of queries they ran and divide it by the amount of electricity they bought. Or maybe his dashboard already shows energy cost per query.

His source is obviously knowing the actual figure. The arXiv paper needs to justify its guesswork.

The reliability can be increased by getting an independent audit. But an audit doesn't change the source being Sam himself.