Keep in mind that they’re talking about hardware control systems and not compute nodes. On these machines, the savings would probably not be too big (no/few consolidation gains). It also sounds like the decision was less about the upgrade cost and more about avoiding failure risks.
I also ran the numbers for fun. They estimated the cost to be 5.4MCHF for 2200 machines. Assuming 0.2CHF/kWh, they would need to save 140W per machine for 10 years to offset the upgrade cost. So, yes, it could indeed offset a good part of the upgrade cost over time.
Keep in mind that they’re talking about hardware control systems and not compute nodes. On these machines, the savings would probably not be too big (no/few consolidation gains). It also sounds like the decision was less about the upgrade cost and more about avoiding failure risks.
I also ran the numbers for fun. They estimated the cost to be 5.4MCHF for 2200 machines. Assuming 0.2CHF/kWh, they would need to save 140W per machine for 10 years to offset the upgrade cost. So, yes, it could indeed offset a good part of the upgrade cost over time.