Our gas tank water heater is 15 years old - getting to the time where it is going to expire sooner than later. Question I have for y'all, what is your experience with the tankless water heater systems? How well do they work - can they keep up with 2 people taking a shower at the same time, etc? Any advice on brands? Also, electric vs. natural gas? (or are they all electric?)

Thanks.

I think they are specified based on your requirements. If you want to have two showers running, the dishwasher and the washing machine running its is one size. If you just want a shower it another.

I was very interested in one but found in a retrofit the cost the unit and the installation costs made them uneconomical. However my hot water heaters are inside mechanical closets inside the house. Perhaps a basement installation would be less expensive.

In new construction I think they could be a very good idea. However I was concerned that most of the tankless units I looked at had short warranties.

I have had a tankless water heater for 12 years. Have had no problems with it. I would not go back to a tank heater. Mine is propane and cost pennies to operate.

Same here, the units I looked out required a minimum 3/4" line for natural gas and mine is 1/2" coming out of a concrete slab. Retrofit would be cost prohibitive but I like the concept.

The ones I looked at needed a different vent through the roof also. However I am with you I like the concept, just could not get the numbers to work.

We run two 40 gallon hot water tanks in series, never run out of water! Love it...... the second one in line lasts a LONG time since it does not get the abuse of heating up the water...just maintains. Best decision we made. We looked into the tankless.

My son installs this brand https://www.rinnai.us/

They changed the gas valve and can be vented with PVC pipe
The different gas valve makes it so a smaller gas pipe size can be run to it
All on demand water heaters require an annual flush to prevent scaling

so as stated above.
The size you need and cost increase will be due to usage.
retrofitting gas lines can be expensive.
220 volts could be used instead of gas.

But the key thing most people miss is that the units are based on temp difference.
They mostly can only do a 40 degree temp increase as it passes through the system.
That is what you need to check on.
I mostly used them overseas, where the outside temp was in the 70 at night and incoming water didn't get much colder than that.
But if you get 50 degree water coming in and you only get a max of 40 degrees up, then you get 90 degree water coming out of your shower.
not going to cut it for most people.
payback is also a hard pill for most to swallow.
An installed water heater tanked is maybe going to run 1k depending on how big and fancy it is.
A tankless unit that can accommodate 2 showers and maybe laundry is going to cost well over that just for the unit.
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Rinnai-RU199IN-Temp-Map.pdf
this one says it can handle 35 degree water
https://www.supplyhouse.com/Rinnai-...QPg7-gI3ubQpnrCqphMTw_o78z0aAgJ2EALw_wcB
but it runs 1700 just for the unit.
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Rinnai-RU199IN-Product-Overview.pdf
at the bottom shows the delta it gets based on flow.

All the water coming in from the main is COLD water. My water heater is used to heat the cold water. I don't understand why people keep calling it a HOT water heater.

We have well water & this time of year it is COLD. A 40^ increase is not going to cut it for us unfortunately. The size unit we have right now is going to cost 1k, without installation. One of my BIL's is a plumber, so installation is not a worry.

The other thing to consider is the hardness of your water. Tankless water heaters don’t last with hard water. We had our whole house replumbed a few years ago and I asked about going tankless. Plumber talked me out of it and into a recirculating pump instead.

the one I linked at 1700 bucks will do a 100 degree delta at 4gpm so it would be plenty for a modern shower, maybe 2.
but as I metioned it is expensive compared to a standard heater.

In the past I ran into a minimum flow rate issue at a client's house. I needed just a bit of hot to amke the water come out around 78 degrees. After a bit it would shut off, registering too low a flow rate to keep heating. I think current units handle this better tho

They're great if you're only a couple people using it and minimal hot water use but if you've got a full household tank is better.

I just installed one in my guest house, it’s a great space saver with unlimited hot water.

You will see the performance chart for your unit will tell you what sort of delta-T (temperature rise) you will get at various GPM and incoming water temps. The newer units are much improved in terms of efficiency of the earlier ones. I couldn't imagine doing one powered by electricity though. I don't have natural gas available in my area and the electric one I looked at would consume I think 120amps when running. Between that and my furnace it would be a problem for only having 200amp service.

I thought the main advantage of the tank vs tankless is, its mainly a point of use solution, ie, you get instant hot/heated water, and you are not heating water running thru uninsulated pipes, over a long run, meaning smaller tankless at as many locations as you have/can afford, and you don't need to constantly maintain gallons of hot water away from its point of need.

Tank all the way! Call me crazy, but I like the idea of having 50 gallons of fresh water sitting in my house. Its a nice to have if the SHTF.