They told me that commercial/industrial rates were higher than residential, so they're either lying or insane. They also said they won't give an industrial rate to a residence.
But what if you do your business in residential area? In large European cities many small businesses are located in multistory buildings where people also live, just occupying one of the apartments (usually on first floor).
I don't know what electric prices they pay, but I think industrial because our supplier offer only two variants: "household" and "business".
BTW, professional miners could consume a lot of power which is more than grid's capacity for apartments, so upgrading to industrial consumer and extra cabling is inevitable.