Are you thinking there is no way you could have used all the hot water? Or perhaps you turned the hot water on 30 minutes ago.
Well unless you have been using more than normal or left the hot water tap running then its quite possible there is a hot water problem that needs investigating.
As water is heated dissolved minerals such as magnesium and calcium precipitate and are deposited at the bottom of the tank, creating a layer if sediment.
As time progresses sediment can take up a lot of space in your tank limiting the amount of hot water it holds. Hence why the hot water runs out quickly.
If this is happening you may notice visible sediment in the water or unusual sounds coming from your tank as well as hissing or leaking from your TPR valve.
Most electric water heaters have two heating elements. One on the bottom which does most of the work. Cold water enters the bottom of the tank and the bottom heating element heats the water which then rises to the top.
The top water heating element maintains the water temperature at the top. Therefore if the lower water heater is faulty then you will notice a considerable drop in the water temperature.
This can be caused by a build up of sediment, a faulty thermostat or an electrical wiring problem.
The job of the dip tube is to push the cold water in the tank to the bottom of the tank. When this tube is not working properly then the cold water stays at the top.
The problem with this is, the hot water rising to the top then mixes with the cold water reducing the over all temperature of the water tank. This means that when you turn on the hot water tap, the water will be cooler.
Mineral build up can cause damage to your water heter. One way to avoid this is to use an anti-scale device. But how does an anti scale device work I hear you say?
The device creates movment of the water at the bottom of the tank and with the water moving mineral build up is less likely. Over time this prevents sediment from building up and causing damage to your tank. An anti-scale device is not the be all and end all.
There are many other reasons why your tank may become faulty over time. Therefore if you have a good water tank and a long warranty then there may be no need for an anti-scale device.
Your choice of fuel type will depend on your property. Many city properties use gas and electric water heaters while more rural properties and older city properties use oil heating. All have many advantages and disadvantages over each other.
Which will offer different levels of efficiency, environmental impact and convenience etc. This is a whole other subject matter which we will not get into here, but definitely worth considering.