I would suggest a single piece of art or a diptych art set.

Not sure what your motivation is but it can be trickey to get a tankless heater installed correctly and they do require regular maintenance.

For your location, I would be strongly attracted to installing a solar water heater that feeds into a electric tank heater.

In choosing a tankless hot water heater, the single most important consideration is availability of factory-authorized local service professionals. Check with a couple of local plumbers to see what brands they service and what their experience has been.

Thanks Jake The Wonderdog. I am trying to understand more about venting as I am brand new to tankless. Condensing VS Non-condensing, differences ?

Hi RJ,

Let me back up:

You install a tankless heater inside the house (in climates where it gets below freezing) or you have the option of installing it outside the house (only in places that won't freeze).

In your location, outside is an option.

If you install it outside, venting isn't an issue (it just exits a slot in the heater) If you install it inside, you have to run a vent to the outside.

There are two general levels of efficiency in gas tankless water heaters (and gas furnaces). That is ~ 82% and ~ 92% or better.

By definition a water heater that is less than 92% is non-condensing. That means the flue gases are not cooled below the saturated vapor point. These type of units don't need a drain for the flue gas condensation but they require special stainless steel flue that is very expensive.

On the other hand, a condensing unit is about 10-12% more efficient because they extract so much heat from the flue gas that the water vapor in the flue gases condenses. They require a drain for the condensate. But because the flue temperature is so low, they can vent through plastic pipe (which is cheap) rather than stainless steel pipe.

I had a non-condensing tankless hot water heater installed on the exterior of my last home. It didn't require any vent pipe since it was outdoors and was direct vent. It lasted 12 years with zero maintenance. When it failed, I replaced it in kind.

It had an internal heating element that protected the heat exchanger in the event of freezing weather--which we experience a couple of weeks/year.

The installed cost difference between condensing and non-condensing type tankless units is significant. Make sure you're aware of all the costs so you can make an informed choice.

Indeed, most tankless heaters include an"emergency" electric heater to prevent the the heat exchanger from being damaged by freezing. That heater should be a fail-safe. Don't install it outside if it gets below freezing.

The difference in cost of the unit (not installed cost) is about $400.

If you have an indoor unit, that cost is negated by the stainless steel venting. If it's outside it may be a different story.

What I currently have

So, why do you want a tankless unit? It seems that durability is a big priority for you, is there any other reason?

Hi Jake The Wonderdog, below factors are what I have in mind and appreciate any feedback. I guess tankless costs less energy over the long term(plus units are said to last longer ?), it's safer as it doesn't hold hot water(but I guess tank these days is generally safe enough), tankless takes up less space as I kind of need extra space for waster/dryer. The existing vent goes thru the roof as seen in the pictures so I wonder if it's a good idea to keep and utilize that for the new tankless.

Thanks for that RJ.

You are right about most of the things you mentioned. Gas tankless will use less energy, they take up less space and they do last longer - especially if you don't have hard water.

There are downsides: They take longer for hot water to get to the faucet (5-8 seconds longer), they are often stupid expensive to retrofit, and gas supply, in particular, can be a problem.

I don't consider the "tank" issue to be that much of an issue - because if a water heater opens up (catastrophic failure) it's not the 40 gal in the tank, it's the 12 gpm from the supply line that's a problem.

What I didn't hear you mention was that you needed continuous hot water - which is one of the big selling points for a tankless heater.

You can't re-use your existing vent other than the actual hole in the roof. You can't use the metal flue with either a condensing or non-condensing unit.

You live in S. California. Water is an issue - so I'm not sure that running water while you wait for a tankless to get hot is a good plan.

I think you should at least consider a hybrid electric heater. They pull heat from the space around the heater and usually cost less to operate even than a tankless gas. They are typically cheaper to install and will not increase the wait time for water. They pair very nicely with Solar (PV). They do use a tank though - so there would be no space savings.

They do output cool/dry air which would be a bonus for you.

BTW: There are probably significant rebates ($500-800) for installing a hybrid electric heater in your area.

Thanks Jake The Wonderdog. I am aware that it takes time for hot water to reach faucets with tankless, but I don't know how bad it will be. I never have problems with running out of hot water with tank so I think I should be ok with tankless. Given the same amount of hot water demand, would higher GPM tankless shorten wait time at faucets for hot water ? Would higher efficiency tankless shorten wait time for hot water also ?

The answer to both of your questions is no. Higher GPM nor Efficiency will change the wait time. Besides, I recommend that you stick with the 200k btu/h and condensing anyway - so there isn't any larger / more efficient.

If you have a home with the master bath at the other end of the home, I would really re-think this.

If you don't have the gas meter close to the water heater location (for 200k btu/h you will need to run at least 3/4" pipe) you should re-think it.

If you aren't prepared to spend $3-4k for this, then you should re-think it.

I think gas tankless are great in the right situations. Specifically they can solve venting problems in older homes that have an unlined masonry flue. When I've done that I also have done a complete re-plumb and moved the heater closer to the end use.

They can also be a good solution in a new home if it's designed properly and avoid some of the retrofit costs.

I don't think you have a great application to be honest. You have a ton of space and it would work really well with a hybrid.

Thanks Jake The Wonderdog. I just came across another thing to consider. It looks like if power goes out tankless can't generate hot water and I wonder how to deal with it. An emergency generator ?

I've been looking at below two. 2nd one has built-in re-circulation to reduce wait time for hot water at faucets. I wonder your thoughts on that.

https://www.homedepot.com/p/Rinnai-Super-High-Efficiency-Plus-11-GPM-Residential-199-000-BTU-Natural-Gas-Interior-Tankless-Water-Heater-RU199iN/306655613

https://www.homedepot.com/p/Rinnai-Super-High-Efficiency-Plus-11-GPM-Residential-199-000-BTU-Natural-Gas-Interior-Tankless-Water-Heater-RUR199iN/306655625

@Jilly Jane - seriously?!? because it says the max gpm is 1.5 and max temp is 116 F.

That's enough hot water to wash your hands. And that's it.

It's electric resistance heat - so all of the drawbacks of that including the cost to operate.

It's good for a very limited application - hot water at a sink where the main water heater is too far away - such as a powder room - or a cabin that gets very little use.

There are much better options.