My hot water runs out quickly, what is the minimum amount of hot water should I expect from my landlord in NYC?

My hot water runs out quickly, what is the minimum amount of hot water should I expect my landlord to provide in NYC? Is there some standard applied? We have 4 people living in an apartment, and it takes 1 brief shower to use up all the hot water. I'd like to confront my landlord about it, as our unit has its own water boiler. But before I do, I'd like to know what the landlord is responsible for providing. Thanks!