Heat pumps can actually be over 100% efficient if you’re measuring it based on heat produced. Because heat pumps aren’t designed to produce heat; They’re designed to move it around via refrigerant. And if you can use 1w of energy to soak up and bring in 3w of heat, you’re now 300% efficient.

So by that metric, a server would be a “bad” heater. It would still contribute to your heating, but not as much as a heat pump would. It doesn’t mean the device is below 100% efficient, it just means the bar for “good” heaters is much higher than 100%.