Hot water heaters

According to the US Department of Energy, water heating accounts for about 20% of the energy use in your home.  There are many things that you can do to reduce the amount of hot water you use, but maintaining your water heater is also very important for saving energy.  There are many types of water heaters: demand or tankless, solar, and storage, to name a few.  A single-family storage water heater offers a ready reservoir -- from 20 to 80 gallons -- of hot water.  In the US, these storage water heaters are in wide use, although the tankless and solar water heaters are becoming more popular.  If you are selecting a new water heater, do some research on the various types to see which is best for you.  If you have an existing storage water heater, proper maintenance will help it perform more efficiently and last longer, both important in saving energy.  I found good how-to resources for storage and tankless water heater maintenance.  Also check the temperature setting for your hot water heater.  Most information sources recommend 120 degrees Fahrenheit so that the water is hot enough for most uses but uses less energy than higher temperature settings.  Temperature settings below 120 degrees Fahrenheit are not recommended for safety reasons. 

https://www.thisoldhouse.com/plumbing/21016402/how-to-maintain-a-water-heater

https://www.wikihow.com/Maintain-a-Tankless-Water-Heater