Homeowners should pay attention to the capacity of their water heater, its physical condition and location. Gas and electricity are two common energy sources for water heaters. A flame at the bottom of the tank heats gas units. A crown shield distributes heat between the flame and tank. Electrical units contain heating elements in the tank.
Electric heaters are more efficient than gas units, but take longer to heat water.
Electrical units also cost more to operate. Efficiency means a greater percentage of energy is applied to making heat rather than going to waste. Blow says the ability of a water heater to heat water quickly is important. Gas units can heat a full 75-gallon tank in one hour. Electric units take as long as three to four hours to heat a full tank.