For our water heater, I think the delay is more along the lines of 30 seconds, which is minor for a shower but it seems like an eternity if I just want to wash my hands. I’m still relatively happy with ours though; it definitely lowered our utility bills.
Do you have one of those recirculating valve thingies?
Not that I know of.
I’m wondering if someone gave me such a system for free, would it be both complimentary AND tankless? 
Tldr: they are better than they were ten years ago but still not ready for prime time.
In a condo with units surrounding you? Sure. But in a climate like Chicago where the incoming water temp can be in the 35-40 degree range for a good chunk of the year they simply can’t handle the needed 90 degree rise reliably.
Most quality units now have the isolation valves built in so servicing is not the disaster it once was.
Also need to factor in how thirsty the gas units are. At 199kbtu, that’s eating a lot of gas. Figure on upgrading your incoming supply to 1” back to the meter.
Depends on the heater. Rinnai recommends that the unit be flushed periodically with vinegar. It also has a sensor that determines if a flush is needed, though I’ve never seen this sensor indicate that a flush was needed. My water is not soft, but it’s not all that hard either.
I do mine once every two years or so.
My Rinnai runs on propane and supplies my 3 bath house perfectly, even when two showers are running at the same time. It takes only 10-15 seconds for hot water to get to any part of the house - just about the same as a tank system.
Yes, it was pricey, but worth every penny.
For what it’s worth, I live in Toronto and I have had no problems reliably getting hot water (i.e. hot enough to shower with) on cold days.
The tankless heater we have is a model popular in Scandinavia where they have to deal with pretty low temperatures.
The heater is set to deliver hot water at around 60-65ºC. This will somewhat depend on the temperature of the incoming water supply - the air temperature has no effect at all. Even if the incoming supply is very cold, it will still do its job. Obviously, if it drops below 0ºC you have a serious problem and not with the heater.
In practice, it is easy to regulate the temperature at the tap. If you want it hotter, just reduce the flow.
The comment above about dishwashers etc is true. You need appliances that heat their own water - it’s more efficient anyway.
We moved into a place with one. It’s funny the upstairs shower warms up quicker than the shower closest to it. Does take between 10 to 20 seconds to warm up.
I wouldn’t say so much “experience with”, as “experience about” We had a water heater that was slowly dying a few years back, and we looked into the gas tankless heaters since we have gas already.
The big issue is that they typically require larger gas lines than homes typically have. IIRC, our house has a 3/4" gas line, and tankless water heaters require at least a 1" line. So installing a tankless water heater wasn’t just a matter of getting a heater, and the relatively minor job of plumbing the gas and water to it where the old heater was, but rather re-doing the entire gas line from the meter to the house AND plumbing 1" line all the way to the water heater itself.
It would have been a much larger job than merely installing a new tankless water heater where the old one was. Like on the order of $4000 to do that, plus the cost of the heater itself.
We had a tankless system put in back in Sept/20. One western Canada winter later and it performed well. Once the water is hot we’ve never run out. Biggest drawback is it takes a minimum of 90 seconds to get hot water if it hasn’t been running such as overnight.
Fortunately, I have a 1" line already running into the attic. It tees off into 2 3/4" lines. One goes to the furnace and another to the fireplace that I rarely use.
We have a Rinnai heated by natural gas, and a whole house water filter and a non salt water softener. We’re on well water in Michigan.
Once installed there’s no maintenance or salt bags to handle.
Twice a year we change the hot and cold filters and flush the Rinnai using a solution designed for tankless. Used to use the vinegar flush but it was too harsh I believe in components. Anyway it’s been about 10 years we’re quite satisfied with the set up. Yes we get code 10’s when it’s past due on a flush. Reduced water pressure occurs first and that’s our cue to get ready to flush. We e got great tasting well water with lots of minerals.
I assume you can’t put it in the same place as your electric heater because a gas heater needs a flue. Is that true?
There are tankless heaters that mount on the outside of the building. They don’t need an exhaust flue, which can simplify installation, although building codes may limit where you can put one (not too close to the property line, for example). Would that be feasible for you?
I have two at the shop, and they make a huge difference when you are washing dogs all day.
Had one of the biggest tanked water heaters we could get, I think 60 gallons or so, and would be out of hot water well before noon.
Now it just goes all day long. They also take up much less space. The two of them take up much less floor space than the on tanked heater did.
My water heater at home is getting on the old side, and I think I will probably go tankless to replace it.
People sometimes say tanked units have a 10 year lifespan, but I have never replaced one that often, nor do people seem to do so. Maybe electric units burn out faster? It’s mostly gas around here, and they seem to typically go 20 years.
I’ve been told that electric or gas heaters last much longer if the anode rod is replaced periodically.
A lot of people decide to replace their hot water heater well after it’s useful life, as they replace at failure. For some regions of the country, builders put the hot water heaters in the attic. A busted leaking hot water heater in an attic is a recipe for disaster. My recommendation to people that don’t need to added costs of a leaking hot water heater is to just replace them every 10 years, and not wait until they fail.
I intend to put it in the same place as my current water heater. It will just need a gas line run to it and it will also have to be vented through the attic and roof.
Since we have a slab and all of the plumbing is in the slab, an external water heater wouldn’t really work for us. The water comes into the house in the closet (in the garage) where the water heater, softener, and whole house filter are located.
That’s pretty much all that is used in Thailand, tankless water heaters. They work pretty well. But make sure it’s installed correctly. Seems like once a year or so the news there would have a story where someone got electrocuted, but I never knew anyone personally that that happened to.