Help with hot water system piping

This is my first post on this site. Could someone point me to a drawing that shows a hot water system using a newer tankless water heater? I have a single story home in Carlsbad, CA and my piping is all in the attic. There are three of us living here and my gas bill averages 33 dollars per month. After calculating the cost of the install, I will determine if it makes sense for me. I am older than dirt. Do these systems use a circulating pump with a return line from the farthest fixture from the water heater? I have been retired for 16 years and things have changed since I was active in the trade. Thanks for your help.

Tankless water heaters can be piped in with or without return lines, just like tank water heaters.

If you are only looking at tankless for the cost savings, and you are spending $33 a month on gas, it doesn't financially make sense to go tankless. For the sake of argument, let's say a tankless unit installed will cost you $1000 more than a tank. And let's also say that the tankless will magically lower your gas bill to $0. It would take 2 1/2 years to pay off. Add in a flush or two, and it would probably take 3 years to pay off. Obviously, you would still have a gas bill, so it would take even longer to pay off.

tankless conversion often require upgrades to the gas pipe size, vent replacement and more maintenance. I heard that technology is going to change soon and the way they are made. more efficient any easier to retro fit into an existing tank location with out excessive modifications. But I don't know the details on that at this time.

Thanks for the reply. I will be watching to see if new technology and pricing comes about.

Mr_David said:

tankless conversion often require upgrades to the gas pipe size, vent replacement and more maintenance. I heard that technology is going to change soon and the way they are made. more efficient any easier to retro fit into an existing tank location with out excessive modifications. But I don't know the details on that at this time.

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Actually, that day is already here. Noritz has a tankless meant to be a direct replacement for a 40 gallon gas tank. Water connections on the top, but gas connection is still on the bottom. It comes with 35' of flexible flue piping that can be pushed through the existing B vent, and a gas valve/burner system that will work with 3 1/2" WC.