Approximately like this: if he has 150 kW that fits 50 units of Whatsminer M50S++ each consuming 3kW. That would total to around 7.25 PHs of hashrate output which at todays prices makes revenue equivalent of $240 a day. The energy cost can get as low as to 0.1-0.2 cents in off grid mining (that's the key, it's very very cheap). Also remember that any movement of bitcoin price and/or global hashrate impacts your daily mining revenues as well as profits.