> for having spare capacity to allow time/location shifting
Part of that calculation should be the amount of compute capacity headroom you'd choose to have anyway even if you didn't care about carbon.
Compute demands can vary from one day to the next. Maybe tomorrow people uploaded 3 times as many YouTube videos as they did today. Maybe load varies based on day of the week or day of the month. To some extent, you can smooth that out by delaying jobs, but there are practical limits.
You also want some spare capacity just for safety. Efficient utilization is important, but things like performance regressions or spikes in demand can happen.
Part of that calculation should be the amount of compute capacity headroom you'd choose to have anyway even if you didn't care about carbon.
Compute demands can vary from one day to the next. Maybe tomorrow people uploaded 3 times as many YouTube videos as they did today. Maybe load varies based on day of the week or day of the month. To some extent, you can smooth that out by delaying jobs, but there are practical limits.
You also want some spare capacity just for safety. Efficient utilization is important, but things like performance regressions or spikes in demand can happen.