OpenAI is a money pit with a website on top. That much we know already, but since OpenAI is a private company, there’s a lot of guesswork required when estimating the depth of the pit.

HSBC’s US software and services team has today updated its OpenAI model to include the company’s $250bn rental of cloud compute from Microsoft, announced late in October, and its $38bn rental of cloud compute from Amazon announced less than a week later. The latest two deals add an extra four gigawatts of compute power to OpenAI’s requirements, bringing the contracted amount to 36 gigawatts.

Based on a total cumulative deal value of up to $1.8tn, OpenAI is heading for a data centre rental bill of about $620bn a year — though only a third of the contracted power is expected to be online by the end of this decade.