The efficiency goes down significantly with those temperatures, given that most sources of waste heat are low-temperature (such as datacenter heating water, was

The efficiency goes down significantly with those temperatures, given that most sources of waste heat are low-temperature (such as datacenter heating water, waste water, etc - places where it makes economically and ecologically sane to extract heat). That's the problem even in district heating where temps are ~115C (like in Helsinki). Sadly, reducing the temperature is not an easy task, since many buildings have heating systems designed for higher temps. Even lowering those temps to 80C would improve efficiency of the heat pumps a lot. But it's a big project to get it done and will most likely take a decade or more.