I have a 40 gallon electric hot water heater in my apartment. The hot water runs out after a 10 minute shower, by the end of the shower I can turn the cold side all the way off and the hot all the way on and it is freezing cold. This is a new hot water heater (supposedly) because they replaced both elements and thermostats in the last one and that did not solve the problem. So, how long should 40 gallons of hot water last? And if the problem isn't in the elements or thermostats then what else could it be? The maintenance crew seems to only think it can be the elements or thermostats. I did turn up the temperature to 150 and that did not help.

Citichick, lets do the math together:

You have 40 gln heater. You have shower head that uses 4gln of water per minute. You mix h/c water in ration of 3:1. As you start taking shower, cold water starts pouring into your heater mixing with existing hot water. So the 10 minutes of hot shower is just about right. New elements have really nothing to do with it. They reheat water at the same pace until they burst. It take such a heater about an hour to reheat 40 glns of water.

Heaters are not powerful enough to reheat water in instant. That's why we install tankless heater. These heaters have continuous and endless supply of hot water.

You have very few choices. The least expensive one is to install low flow shower head. They use between 1.6-2.2 glns per minute. Therefore, you will get about twice as long showers. Or install tankless hot water heater.