Eli5: Water heaters, how do they work and the difference between electric and gas tankless vs tank

Question

I’ve researched for hours and am a bit confused with how to decipher the language, lacking context/background knowledge.

Thank you!

(I need a new water heater, wanting to go from tank to tankless. Its currently in the house under the stairs of bottom floor (no basement), 2.5 bathrooms in use (3rd no one uses much), 4 people, 3 story townhome, of any of this info is relevant… not asking for opinion just how it all works)

In: Engineering

Answer 1

Ok, first, you have (3) basic systems –

1) A hot water system that combines a heating chamber with a large storage tank in one unit. These can be (“Direct Fired”) gas (gas can be utility supplied natural gas or a local tank of propane) or electric and might be tied into your home heating system. Direct fired gas systems will corrode over time and eventually leak, one of the most common sources of water damage in a home.

2) A hot water system that has separate heating chambers and water storage systems, since the water storage will get cold you have a loop that circulates the stored water back through the heating chamber periodically. These can be electric or gas and might be tied into your home heating system. These systems are popular since the storage tank is typically fiber glass and won’t degrade or leak, a common problem with aging water heaters.

3) A hot water system that does not have any storage capacity but is integrated directly into the water tap for “on demand” hot water, these are electric. Your home heating system is separate from this. You would need one of these for each tap.

With the first two systems, when you turn on a hot water tap, the water will travel through cold pipes from the storage tank to your faucet and will cool off, which is why it takes a few moments for the water to turn hot. Since the 3rd system is local and ‘on demand’ it heats the water instantly.

For understanding your options you should first understand if you rely on your existing water heater for home heating, that might limit your choices or require you to purchase additional equipment.

In the US central hot water heaters are most common as we typically have the luxury of larger homes with multiple bathrooms and cheap, reliable utilities. From the demands you mention above a central system with a separate tank feels logical. In other parts of the world multiple on-demand electric heaters are more common.