Check that you have electricity gas and water the first rule of solving problems with your boiler is to start with.
Boiler not heating water tank.
In an electric water heater the water is heated by electric upper and lower heating elements that extend into the water tank.
This is the more likely cause if the change in heating capacity has been sudden.
What are the causes of no hot water from oil fueled boilers.
As you turn on the water and set the desired temperature a tankless water heater will heat the water going into your shower or sink for as long as you have the water running.
Check the boiler controls if you still have no hot.
A tankless water heater heats the water instantly instead of storing it in a tank.
Also check the heating circuit fuses and the circuit breaker itself.
Many boiler problems will result in a fault code being displayed in your control.
Gas water heaters have a gas burner that heats the water from below the tank.
The minerals buildup may prevent water from entering the tank as well as making it more difficult for the heater to warm up the water.
Often this issue is caused by the gas supply so check to make sure your propane tank is full before you do anything else.
The main difference between electric and gas water heaters is the heat source.
Is there a fault code displayed.
There are several reasons your water heater could fail to ignite.
Some thermostats control not only the heating but the water heating and a thermostat will not turn on.
If it is out re light it.
Check and open gas and water valves fully.
This is the likely cause if the change has been gradual.
Open the burner access covers and check the status of the pilot light.
These are the common problems for a poorly heated boiler.
If your gas valve or water valves are not fully opened this could also cause the ignition to fail.
The water entering the tank may carry those deposits as well as some other substances which will make it impossible for the heater to work correctly.
If you have a gas powered water heater and the pilot light goes out the water will not be heated.