There are several factors to consider when determining the size of your next water heater. Most people that replace their water heater will use the old water heater to gauge the size they will need. However you should also consider that not all water heaters perform the same. When water heaters get older and collect sediment in the tank it can reduced their ability to heat water.
New water heaters are more efficient and perform better than older units. Also by flushing your water heater annually, you will improve the efficiency and performance of your water heater.
Meeting a heavy demand for hot water
The most common residential water heaters are 40 and 50 gallon tanks. In some cases larger 75-80 gallon tanks are also installed for families that do not have enough hot water. You can also install multiple 40 gallon water heaters which can actually be far more efficient that an 80 gallon tank.
There are also many quick recovery tanks that are available through various manufacturers. A quick recovery tank can cost up to twice as much for the unit and may only slightly improve the amount of hot water produced.