A 40 gallon tank can provide 2 showers per hour. You can get 80 gallon ones for residential use, larger than that is in commercial territory.
But that's still just 4 showers - if you have a bunch of people all getting ready for an event, and you also have laundry to do (which uses double what a shower uses, although takes longer) and run the dishwasher, etc.
It's not enough. You would need a truly mammoth tank.
Instead you have a large fire at the bottom, and heat the water almost as fast as you use it, then you don't run out.
A heat pump water heater would simply not work for a 6 person home in the north in the winter.
Congratulations on creating a scenario in your mind that will never happen. If you are all less than an hour away from leaving for an event, why are you washing clothes that won't be ready in time? Did you really have to run the dishwasher right before Kim's wedding or could you have set it to run while you are gone or after you get back if you somehow have a dishwasher without a timer setting? If you know you need four people to shower, maybe don't all wait until the last minute.
But that's still just 4 showers - if you have a bunch of people all getting ready for an event, and you also have laundry to do (which uses double what a shower uses, although takes longer) and run the dishwasher, etc.
It's not enough. You would need a truly mammoth tank.
Instead you have a large fire at the bottom, and heat the water almost as fast as you use it, then you don't run out.
A heat pump water heater would simply not work for a 6 person home in the north in the winter.