Yes, with a more efficient CPU, you consume less power and generate less heat. No disputing that. But it takes a long time and many kWh to burn up $100, as an example, in electricity. A 100W lightbulb burning at full power constantly for 10 solid hours would consume just 1 kWh, or...
You’ll need to generate enough oxygen and food to keep your colony going, which requires assiduously managing gasses, liquids, pressures, electricity and frantically Googling things like “layout for plumbing system.” By the time you’ve figured out something is wrong, it’s basically too late...