We're going through this debate ourselves currently.

Our biggest hurdle is how the new efficient dishwashers interact with the lack of instant hot water that is NOT coming from the tankless.

Would rather not have to put in additional equipment ($$) for to compensate for this issue.

Everything else says there are some marginal albeit small gains to be had but failure to get things 'lit up' for the dishwasher will be a deal killer.

I'm confused. Isn't instant hot water what going tankless delivers?

@tartanhabit: intuitively - do u see where hot water would be stored for you to get instant hot water?

Physically instant hot water would mean that it has to be stored somewhere in big quantity ie a tank - where it stores constantly heated water.

vs.

Tankless - Heats cold water with a gas burner or electric element as it passes through the water heater.

Which one do you think gets up @ running right away? The tank.

Big advantage of tankless is that once you are up & running you will never run out of hot water. But the delay as much as 2 mins may cause trouble for a few things such as newer high efficiency DW's.

I will merely remark that with a conventional water heater it takes more than two minutes for the water in my kitchen area to become hot.

Delivery of hot water to any point has much much more to do with location of the heater than the type. If you will have issues with purging the lines of cold water for your DW's fill cycle, then you will have issues with whatever type of appliance produces that hot water. The easy solution, and the one I employ, is to run the hot water at the kitchen sink right before I turn on the DW. That preloads the (hopefully) insulated pipes with hot water in enough of an amount to work with any DW. The biggest culprit to poor performance in modern DW's is the new phosphate free DW detergents, not tankless water heaters.

I've lived with a tankless for almost 20 years with zero issues with my DW, showers, washing machines, or any other hot water using application in my home. (Yes, the same one, never replaced or even needing more than basic 5 minute service.) I have an older model Myson with lower capacity than many new ones, but it suits my two person household's use just fine. We practice hot water usage in sequence most of the time anyway, so simultaneously needing to run a shower and the washing machine rarely happens. But, in summer, with the higher incoming water temperatures, it's not a problem. In winter, with the lower incoming water temperature, only one large use application can be done at one time. But, that's not a big behavioral alteration to acquiesce to for the saving's we've enjoyed over the nearly 20 years of use.

The big bonus is that I can enjoy a 20 minute shower massage pounding on sore muscles, and then so can the other half, or any guests we might have. There is no waiting on a tank to "recover" from a high demand use, like I've filled the tub so now can't wash a load of white kitchen towels.

The big downside to most tankless as a retrofit is the high labor costs associated with it. It's not "plug and play" like it would be replacing a tanked with a tanked. You'll probably have to upsize your vent and your gas lines. That doesn't usually come cheap, unless you can DIY some of the labor. That translates into a long payback period, which for much of America that averages moving every 5-7 years, means that you won't end up seeing the savings in the timeframe that you own the home. If this is a home that you plan to live in for a long time, it's probably worth it to you rather than replacing a tanked for 2-3 times during the same time frame.

@ tartanhabit: below thread should give you a good view of all the points in your quest.

Yes - how your house is configured & if it's gas/electric are on top of the small issue I previously brought up.

Good luck on your research!

Here is a link that might be useful: Tankless issues

I don't have one, but the biggest complaint I've heard is that when the power goes out, so does your hot water. At least you still have some with a tank...for a while anyway. This was pretty important for us when we were without power for several days after last year's tornadoes wiped out power for almost a week. We had a generator for most appliances and a warm shower was better than a cold one! If you don't have frequent power outages, then this may not be a concern.

Pros--
> Uses 1/4 the energy of a full suzed water heater-- gas OR electric

> (this one would be all it would take for me) UNLIMITED HOT WATER!!!!!

> A standard hot water heater takes up the room of a 55 gallon drum, floor (almost) to ceiling. Tankless heater takes up the room of a large clothing gift box on the wall.

> Because of the fact that it's an energy star heater, it's also atleast partially tax deductible

Cons

>Initially, it's more than 3 times the expense of buying and installing a standard water heater. However, that's MORE than paid back by the energy savings.

pbx2, thank you - I did not mean to come across a complete nitwit with the 'instant' comment :-) I guess I've been reading a lot of literature about hot water 'on demand'. Our DW is not that old either, so perhaps this is something I need to be aware of too. How can I tell in advance if it will be a problem?

Boy, that was a spicy thread you sent me over to, but some useful information nonetheless. Thanks.

Live wire oak, thank you too. Yes, we have a similar usage/set up; just the 2 of us, tend to use water in sequence too. I guess I've just got used to crappy pressure from old pipes (soon to be replaced) so I would never dream of running the dishwasher and taking a shower at the same time!

Thanks for chiming in Bill! Unlimited hot water would be nice. I have a few chronic pain issues and although I'm mindful of water conservation and all that, a good deep soak is sometimes just the thing I need.

This does feel like quite a change and quite a big leap to make in that direction.

We installed one in our lake house a few years ago and I love not having to worry about who spends how long in the shower. My thought about the "delay" was the same as mentioned above - that it took forever for my water to get hot using the old conventional water heater. Also, don't the newer dishwasher heat their own water?

I've got a sister who lives in Southington, Ct., and I look forward to staying with her when I go down, just for that reason. I LOVE standing in the shower and letting the hot water wail on me for a 1/2 hour, and not worry about it.

@ tartanhabit:: hope I didn't sound snarky. I'm in this for the research for our setup also.

I'd rather be wrong & educated about it than be making assumptions running off with it.

So far, I think we are getting useful data & at the end of the day it may come down to how well you know yourself & your house.

There is no right answer IMO. The savings economics has not been clearly shown to me yet though.

I love ours that we've had for several years. Our plumber wants us to upgrade to larger copper diameter pipes to deliver the water to our bath better. But we still have our old smaller diameter pipes. My DH thinks about it from time to time though. There is a delay but there was with our tank too. We had electric H2O tank heater so we had to change to an LP line to get our tankless installed. I love it. We have a Navien.

pbx2 - not snarky, thanks! Keep us posted about what/how you decide.

We have 2...one to serve each side of our house (long ranch). We are very pleased with their operation. Only difference is you can't trickle hot water into the bathtub like I used to...it needs to be on or off.

Dishwasher and clothes washer issue--like live_wire_oak states, running the water at the nearest faucet until hot will fix the issue of cold water having to run through the lines first. Another fix is to install a circulating pump when you put in the tankless--some now come all in 1 unit. A circulating pump really does equate to instant hot water--it takes 4 seconds for super hot water to reach our master bath which is clear on the other side of the house from the hot water heater.

As far as power outages go, unless you're going with an electric tankless water heater, it should not matter. NG or LP gas don't require electricity.

The benefit of never-ending hot water is an awesome thing! DH likes to take really long, hot, steamy showers and now he can without having to worry about whether or not there will be enough hot water for the next person. Same goes for when I fill up my big tub and have a relaxing bath.

We made the switch to tankless with our new build and I am very happy we did. I would definitely recommend it.

Hope this helps!

@mydreamhome: some very interesting points you brought up.

1) How far is your water traveling for it to only take 4 secs to your bath?

2) The tankless+circulating pump - how much addl cost are you talking about here? Separate or all-in-one wise?

Just a note, while our tankless is LP heated, it does have a computerized component that needs to be plugged in. It will not work unless it is plugged in.

We really wanted one but the travel distance plus the delta temp nuked our plans. Our water enters the house at 37 degrees in the winter! So we would have needed a monster!
We went with the hybrid system by Smuth. It is several years old now and has been terrific!
It was called the vortex but maybe the changed model names. We have never run out of hot water and can run DW, washer, and 2 showers!
50 gallon tank but can create over 100 gallons an hour!
It qualified as a high efficiency so received a nice rebate and tax credit!
Our gas runs ,6 CF per month to run the hot water and dryer! And DH loves to do laundry and takes super long showers!
I looked into a bathroom boost to have a small on demand just for the sinks but it takes time to heat the water anyway, so just insulated the pipes. Not sure the insulation changes much but was hoping to decrease time to reach bathroom. Not sure this last part makes too much sense

Thanks a2gemini. I found a 'Smith' vertex brand online but looks like you can only order it through a sales representative here in NCal - they don't seem to be represented in any of the big plumbing stores. I like the concept though.

We got ours through a local HVAC installer.
Good luck!
I really wanted the tankless but just not in the cards!

pbx2- Our circulating pump was separate component because our plumber did not carry the ones that have them built in. If I remember right, it ran $600 installed. I want to say I found the all-in-one unit on eBay originally and researched it from there. I posted a link to the brand I think it was.

Our master bath is approx 56' from the tankless hot water heater. The 4 seconds is with the recirc loop running. the loop has a timer on it so you can set it just to recirc at certain times if you want. That's how ours is set right now. If you're running the hot water when the recirc is not running, it takes approx 60-120 seconds depending on outside temps.

Hope this helps!

Here is a link that might be useful: Eternal Hybrid Water Heater

Revivig n older thread as quite applicable. We have a 20yr plus LP tankless which is on it's way out and creates problems when it needs a new valve or thermocouple as no one wants to work on it. Debating whether to stay with tankless (we may need to upgrade gas lines for the newer ones) or move to a high efficiency traditional. Reasons are 1.cheaper up front cost (selling house in next year or so), 2.newer traditional heater are just as energy efficient.
3.we have well water so need a power supply for the well pump-so outages not an issue-(PLUS gas tankless heaters have electric ignition and venting fan),
4.our tankless has always been a little quirky and not sure if part of the problem is that we don't have brilliant cold water pressure to start with so if 2 water appliances running together the water flow to the heater drops and it cuts off
5. I have a new HE washing machine and can't get anything close to a hot wash with the tankless. The washing machine on a warm wash setting draws from the hot water supply in very short, sharp bursts. The water heater fires, but before it has chance to have any effect on water temp, the washer stops drawing hot water! I don't like this because I like to wash things like towels and sheets and underwear on a hot wash for hygiene and dust mites etc. I've noticed that towels in particular don't smell clean. I am trialing pre-wash v extra rinse v pre-wash and extra rinse to see which might help.
Any ideas? I've not had a tanked water heater for 20yrs as originally from England and had a combination gas water heater and heating systems (via radiators). These were higher tech, but more to go wrong . Difference was that ours was in the kitchen, right next to the dish washer and washing machine and the one bathroom we had was directly above the kitchen. Still I used to notice that I never really got a hot wash on the washing machine, until I changed to a newer HE that was cold water fill only.

We have had our tankless or 3 or 4 months. (Only two of us in the house). I love the unlimited hot water. We just did a major remodel to one of our baths and now I can truly enjoy the shower without fear (though I don't do a LONG shower every day - water conservation and all that - but it is VERY nice to have the option.)

I also have heard about running a faucet adjacent to the dishwasher. I do that before I start my washing machine but my only requirement is that the first fillup is hot, not so picky about the later refills during the cycle. Don't have a dishwasher but will soon, I'll definitely keep this issue about "hot water cycles" in mind when I shop. (Probably will post on GW for input from others too about which brand is best.)

We are in a major metropolitan area but I still had some concern about maintenance. (Ours is gas and installed outside our back door so chose the "external vent" model.) Lots of plumbers want to install tankless water heaters. I don't fault them but I wanted to make sure to get someone who knew how to size our needs and knew what issues they might run into.

I found out where the nearest Rinnai parts distribution center/sales office was and found out they did tankless water heater installations using their own plumber. That means if I have a problem, I call the guys who everyone else also calls (for the most part.) Somehow that gives me some peace of mind though I'm sure there were other great installers, I just didn't know who to pick. Always get a couple of bids of course and these guys were in the middle.

They were legit and required the permit. Turns out we had a gas leak so glad they were following the rule book. We had to call another plumber to fix the gas leaks (more than one :( ) and wasn't cheap since they had to hunt in crawl space under our house for more than a day but REALLY feel good about the whole experience.

FYI - You can buy a backup for your waterheater that can have various time windows. You plug your water heater into the backup and then the backup into your electric outlet. We haven't done this since if our power goes out, it is a very short time except in the summer. Then, if there is a hurricane, it could be an outage for a couple of weeks but the weather is so hot in the summer, we don't need hot water for showers. YMMV

Another point to add about our tankless installation is that the company/plumber would not even consider installation until they made sure our gas line was big enough.

Also, because our home is old with lots of galvanized plumbing (which we hopefully will have all replaced soon) , the tankless installer required that the water from the city to our tankless water heater be "clean", hence they replaced that segment of galvanized pipe with PEX. Added more cost but made a lot of sense. Apparently the tankless water heaters can be sensitive. Or another way to think about it, why would you spend this much on a water heater if you were going to input cruddy water coming from 50 year old galvanized pipes? (I'm thinking the same thing about our new shower, hence our planned project to replace all galvanized pipes - new shower has copper but pipes leading to room are not all copper yet.)