Yeah, it's a little off the usual topic content but, My Hot water heater is starting to go. I would prefer to change it before it quits completely.

I've done some research on tankless water heaters but, I would like to here feedback on those of you that have them. I live in the phoenix area so, ground water rarely gets below 45-50 degrees and I have a 200amp service panel. I only have electric

Thanks !


<F body content - I take a shower before going to the race track with my Firebird :lol >

two main concerns.

Do you have electric capacity? a typical unit might require three 40 amp circuits on a 240V system. Unless your home is practically new, and the electric service was way oversized to begin with, you probably don't have this capacity.

Second, the unit needs to be sized to supply enough hot water to meet the flow requirements of the users. For example, if the unit supplies 3 gallons per minute at a 40 degree rise (and your incoming is 50), it will never be capable of filling a 50 gallon tub with 100 degree water since the max temp here would be 90. If you reset the system to supply a higher temp, then the available flow will be less. for example, if you get 2gpm with a 50 degree rise, in this example, you will need 25 minutes to fill a 50 gallon tub with 100 degree water. Not too good.

This type of system makes more sense in an application where space is at a premium, where there may be extremely long plumbing runs, where there is plenty of electric capacity, and where long periods of time pass (measured in many days or weeks) where hot water is not required.

I suspect your local electric utility company would greatly frown on this as well...since they need to have more capacity (about 27kw) to serve your tankless unit than your old fashioned tank (about 5kw). Just round numbers.

I'd stick with old school.

bock

Interesting, and the first negaitve I've read about them. However, most of what I'm read was from vendors.. and come to think of it, the electric ones were only mentioned for an under-sink install out in a shop (f-body content - which is where I fix my f-body), or something similar. All the whole-house units are always shown as gas.. now I know why!

Bock - Does your opinion hold true for gas units as well? Our HW heater is nowhere near dead, but: we have a gigantic jacuzzi tub (drains our 80 gal. HW heater in order to almost fill it), and there's only the 2 of us in the house, so the usage is very much 2x a day. We're also on well water, so we'd need a very good amount of temp rise.

I'd also have to think that it would take even longer to get hot water at the tap with a tankless, since the unit itself would have to heat up?

The typical instantaneous water heater (gas or electric) is placed as near the point of use as possible with the cold water piped to it and the hot supply coming out would be very near to the point of use. The under the sink application is actually a very good one for this type of unit, especially in a shop.

The gas versus electric question relates mainly to the availability and price of gas (natural gas typically, LP gas costs too much) relative to electric. For example, in the northwest where they have a lot of cheap hydroelectric, it is usually way cheaper to run an electric unit. I can do some calculations if given the parameters (cost of each fuel, install costs, maintenance, etc.) but generally speaking in most parts of the country, the gas unit will cost more to install, but less to operate over a long period of time which would yield some sort of rate of return relative to the electric.

Where I live (Florida) well water is about 70F year round so we don't have the same temp rise problems as other parts of the country. Although the point of use water heater sellers would like you to believe that you are wasting tons of energy with the old style storage tank type heater, the truth is there are real significant cost tradeoffs. If you are actually using your hot water twice a day (bathing, dish washing, jacuzziing, or whatever) then the old style tank (gas or electric) is very probably your best bang for the buck, even though it sits there much of the time not being used.

bock

I just moved from a 3 BR house that had an old style NG water heater and furnace. In the summer when I was not using the furnace, my NG bills were like $26/month for 2 people.

Edit: added "old style"

The former (and old) apartment I used to live in - 3rd floor of a three story house - had a tankless water heater that ran off our oil burning furnace. Worked pretty well, never had any issues with water making it to the 3rd floor, didn't seem like it took long to heat up. I also had a water-saver shower head, not sure whether that makes a difference? (f-body content - think radiator hose restrictors/thermostats).

I liked it. I'd consider one if/when I convert from our electric tank heater to propane.

The only issue I had with it was running out of fuel oil in the middle of summer because you just don't' think about it when it's hot outside.

Ask me how I know.

Did anyone see the episode of Mythbusters where they "blew up" a water tank?

I designed my home and had it built to my specs. I knew I was going to add a big shop one day so I made sure I had the electric service oversized to begin with. Gas is not available in my area.

The only area of the house that has a long run is the guest bath in the back of the house that rarely gets used. I'm the only one in the house so theres no worries about usage requirements since they are minimal.

Daily shower, dishwasher maybe once a week (quicker to do most by hand) and 2 or 3 loads of laundry a week? The current "old school" tank just sits there and stays hot most of the time. I wonder if the tankless heater, even though it uses more power when working, would end up saving more because I just don't use that much hot water ?

I've installed a couple of the electric hot water heaters before. (I'm a licensed electrician)

A 200amp service is more than enough unless your panel is completely full of tandem breakers and there is no space left. Be sure to keep in mind where the hot water heater is going, where the service panel is and the possibility of getting electricity to it without spending a fortune. The bigger the heater the more expensive the wiring is going to get there. Unless they have changed recently these units don't perform very well with low flow conditions. IE dishwasher or sinks. Your dishes in your dish washer might always get washed with luke warm/cold water.

Having installed and used them I don't recommend them. You will spend more on the unit and hooking it up then you will save money on electricity. Just get a really nice electric hot water heater and call it a day.

I live in Buffalo and use NG for heating so I have a different application. I love having a tankless hot water heater. I don't save any money with a family of 4 using it but no one ever gets a cold shower. With only one user the savings would be noticed but at what cost? Run the numbers and see what it will cost to run hot water for 30 minutes a day with the tankless versus keeping 40 gallons hot for 24 hours and that should make the answer clear. -FRRAX content- I will be helping rushman install a tankless NG water heater soon.

Your application sounds like a possible winner for the tankless unit. Your usage is low, demand is low, and you can arrange your lifestyle to work with a lower output hot water temp. Check your dishwasher to make sure it has on on-board water heating capacity. Tankless is worth doing some additional investigation including talking to somebody that has one.

Depending on the unit you select, you will very likely need to upgrade the wiring (cost is not insignificant) in addition to the purchase cost of the unit. Also check into the water quality available as the heating elements in these units can scale badly with poor water and require early replacement. The same thing can happen to a regular hot water tank, but the design allows a lot of the scale to collect on the sides and in the bottom of the tank which is not an option with the tankless.

Good luck

bock

My in-laws have a tankless hot water heater and they live in Poland, where it gets damn cold in the winter. It's funny how the economics over in Europe drive technology and energy efficiency alot faster than the US. They have a 3000 square foot home and the house is heated with radiant hot water heat. The heater that heats the house also heats the hot water. They pay over 4x what we pay for natural gas and their heating bill is constantly less than a 1/4 of what I pay and my house is 2000 sq feet. The primary difference I think is that 1. they use hot water radiant heat, and 2 the walls on their house are like 2 feet thick and made out of concrete covered with foam and then plaster and then stucko. The windows are really more advanced than anything I've seen in the US. They are triple pain and were installed over 10 years ago and the seals are more like you'd see on car door, not a home window.

When I first met my wife her parents lived in Communist era condo, so everything was very minimalistic, effective and functional. They had a gas powered tankless hot water heater that was mounted right in the bathroom above the tube. I remember how impressed I was with the instant hot water, and I also thought it was funny that it was made by Junkers, you know, the same company that brought us the WWII JU-97 German Dive Bomber used in the Blitz. All in all, I was impressed, and when it comes time to replace my hot water heater, I'm going tankless.

My parents just installed one of these tankless systems in their. It runs the regular water system as well as well as radiant floor heating. Works amazingly. They can have two showers running, the floor temp set @ 80 and a dishwasher going and it doesn't falter. Fairly large house too, ~8k sq ft. I don't know any of the specifics as far as model and what not but I can find out. Kind of cool to go out and just see a wall of pipes, valves, and guages.

My parents had one professionally installed when their conventional model expired. They were pitched the efficiency story which made some sense given it's a 2nd home. Every service in the house provides the user a different experience. The kitchen sink takes forever to get warm and it may get hot but I've never had the patience to wait long enough to tell for sure. Several of the showers have restricted flow heads and you WILL NOT get hot water unless you let the hot water run in the tub for a while (unrestricted flow). It will get extremely hot if you have enough flow (i.e. in the tub) but if you flip over to the shower head.... it'll go cold again sometimes on you and then you have to open up the tub faucet again to get it hot. Seems like the unit does a poor job of measuring when it needs to be on/off, perhaps an adjustment can be made? All in all I'd say this install completely blows and it would be extremely difficult to convince anyone in my family (or any guest that has stayed here) to go that route again. They'll be installing a tank unit again soon. This is a gas system.

As far as the efficiency is concerned, a friend of mine's brother was convinced the tankless unit he was going to install was going to single handedly cut the US's dependance on foreign energy sources. My buddy doubted him. They made a bet, figured out some way to measure gas consumption over several days of equal use. The old tank system proved to be about 15% more efficient. This was also a gas system.

Perhaps is an entire facility's plumbing is designed around tankless..... they may work better. Otherwise, I'd probably steer clear.

Wow, good read. My only experience with a tankless is a gas-fired unit we had in our 'shack' in Cayos Cochinos, Honduras. It hung in the bathroom just outside the shower. I think it fed our room and the one next door. It seemed to cycle on and off. When it was on, the water was scalding hot, when off, it would cool down significantly. And it would cycle faster when the neighbors were using their shower.

I am going to look at one when it gets time to put plumbing into our shop, so this is a good read. Perhaps a small, well-insulated regular water heater would still be a solution.

Tankless for sure! I installed a Bosch tankless electric in our guest house. The in-laws stay there all the time and they are both "bath" people instead of "shower" people. No issues whatsoever. Sized and installed right, tankless is the way to go.