Today I learned about zombie servers in data centers. 

"Inactive servers (also referred to as comatose or 'zombie' servers), represent obsolete or unused servers that consume electricity but provide no useful information services. Previous studies have estimated that inactive servers represent 10%–30% of servers in US data centers [28–31]." (Shehabi et al., 2018)

I can't imagine that these exist in a bitcoin mining facility. Zombie bitcoin miners sucking up electricity but not generating bitcoin?? The crazy thing is the 10-30% figure for non-crypto data centers. That's a lot of waste.