We just bought a new to us house. The water heater is quite old and will probably need to be replaced in the next year or so. I am wondering about the pros and cons of a Tankless water heater. For 2 reasons. ONe is takes forever to get the hot water to the 2 bathrooms because the existing heater is near the kitchen. It would be really easy to mount a tankless water heater much closer to the bathrooms. We had poor luck with a tankless heater where I worked using it to get water to our Darkroom. The University would shut off the water without telling us and it would kill the heating element. I understand they now have systems to solve that problem so probably would not be a problem in the home.
I had one installed 5 or 6 years ago. It takes awhile for hot water to reach my furthest faucet but otherwise I have no regrets. My gas bill took a huge nosedive. I was heating water 24/7 just so it would be available when needed. Also I never run out of hot water. Costs a bit to install but well worth it.
Suggest you ask: How often does my electrical service fail to deliver? In my neighborhood the answer is: FAR Too Often!! So, if the system depends on electrical power to get it going - - -be careful.. P
If you are on a well, then check how cold your well water is. We found that our input water temperature to be too low for a tankless water heater to work effectively. This was several years ago and things might have changed with the technology.
My knowledge on these things is somewhat dated. The other posters have raised some good points.
Start with: Heat gets out of a tanked water heater three ways: You use it, Stand by losses, and up the flue (gas).
Several things to consider. Small to medium tankless heaters may not provide enough hot water for more than one thing at a time. They have a flow rate and burner capacity that determines how many Gallons per minute they can deliver. OTOH, larger units require a huge gas input to generate lots of hot water and may require a fairly high flow rate to activate the burner. Turn on a small trickle and you get cold water.
I have seen houses that have 150,000 btu burners in the water heater and 80,000 in the furnace. This could require upgrading your entire gas system if you have it, all the way from the street.
The length of time it takes to get the hot water to a location is a function of the distance from the source to the use, not so much tank or tankless.
Time is also affected by pipe diameter, 3/4" pipe takes longer than 1/2".
Exterior mounted tankless heaters must have freeze protection.
You can cut standby losses by insulating the tank and pipes. All newer heaters come with a flow restricter that prevents water circulating into the pipes and cooling off due to thermosyphoning.
I looked into putting a little pump under my kitchen sink to circulate the hot water up to the sink without flushing it down the drain. Kits are available. I was going to use a timer. Push a button and it would run long enough to bring you hot water and shut off.
Electric versions require huge power supplies, sixty amps or more.
Another thing to consider is that your new heater will most likely be physically larger that then old one. New standards require more insulation, a good thing, cutting standby losses, but may not fit the old space.
In my home the gas connection was less than five feet away --a vent even closer and the connection (exclusive if the heater) was $1700 and a inspection by the gas company. In addition, completion was five days. I can purchase two water heaters for that kind of money. I decided I'll live with the gas bill.
Expensed of the unit and installation is what worries me. I can do the electrical.if no inspection issues needed. I would let them do gas since I would need a line run from the road.
John I have a Rinnai tankless. In fact, I just descaled it myself two days ago. The cost of the submersible pump and water lines I needed was way less than what I paid a plumber after the first year.
Mine is a Non-Condensing unit designed to handle four things at once. It uses natural gas and plugs into an electric outlet for power. These things don't pull much current so a 15-amp circuit is plenty.
We connected to the natural gas service, which was free for us from the gas company, and hired a plumbing contractor to install the gas piping from the meter to under the crawl space, install the water heater, connect to our gas log fireplace (formerly propane), and install stub-outs for future gas appliances.
Our gas bill is usually between $15 - $35 depending on if we're using the fireplace. They do have something that aids getting hot water quickly to those faucets that are farthest away if that's a problem.
I had a similar problem with it taking to long for hot water to get to our kitchen sink and the powder room sink. The problem was solved with the installation of a “point of use” water heater under the sink at each location. It took a 30 amp 220V circuit to each location to accomplish. I have not tried this approach for a tub/shower, but there is no reason I can think of why it would not work.
Calculate out how little volume there is in even a 100' run of pipe. Or how little time it takes to fill 100' of hose. The problem is flow, not volume. The problem is readily solved by doing away with the flow limiters the water deficient folks in CA mandated upon the rest of us. With the flow 60 psi is capable of delivering it will not take long to get hot water anywhere if you remove the limitations. .
Before you decide, check your incoming water temperature and determine the flow from your shower head. Then check the charts for tankless systems to determine the size you need that will give you a base price. Installation costs will add to that. Most gas companies will give a significant rebate for switching and their customer service may even help you determine your operating costs based on your family size.
First, a little background as to why I switched to tankless. I had twin conventional Bradford White water heaters piped in series, 40 gal each. The reason for two is because of the whirlpool tub which rarely got used. I had already replaced the individual units four times, so a total of 6 water heaters in a 30 year old home, with one on it's last legs and probably needing replacement within a year or two. I had also changed the twin furnaces to high efficiency condensing units. This left the remaining water heaters orphaned into a now too large chimney flue. With one heater about to need replacing (around $900 installed) and another $700 or so for installing a new smaller chimney liner, the numbers looked better to do the tankless at $1,700 installed.
I have a Navien NPE-240A. The install was pretty simple since I already had the gas line for the two old water heaters and electrical was also close by. Located on an outside rear wall of the basement meant a short run of PVC direct vent piping to the outside too. I'm very happy with the results after living with it for about a year. Had a control board go bad in the first month and replaced under warranty. Last winter we had temps down to 26 below zero with the cold water coming into the house in the 37-42 degree range. No problems with getting the water hot enough. I set it at 130 degrees F and it feeds my dual head shower with no issues. According to the tables, this heater has a capacity of slightly less than 5 gpm at our winter 90 degree temperature rise (from 40 to 130 degrees).
The Navien modulates, so I see no issues with low flows into the sink basins. Earlier heaters had trouble throttling down to low flows and would go hot-cool-hot-cool...... I think all the newer ones have overcome that issue.
The only real maintenance I see with these is a periodic chemical flush to keep the heat exchanger and flow sensor free of mineral deposits. If you have relatively soft water, that shouldn't be necessary more than once every couple years. With hard water, I'd do it annually.
I installed a Takagi gas tankless about 12 years ago and have no complaints at all. Mine is the older style and the special stainless steel type Z venting when I did it was almost a deal breaker but I had no choice at the time (long story). It does take a little time to get all the way to the back bath but it's not that bad. In the last year I have installed 2 Navien heaters both gas for my kids homes. Things are much improved! High efficiency condensing units now use PVC venting, installation is much simpler. both these units have a recirculating mode to prevent the cold water slug in the pipe. First home had a pipe run down from the furthest bath and allowed me to hook up an external pipe to recirculate and the Navien has a setting for that. The other house did not have a return pipe but the unit has an internal recirculating setting that works very well. Naviens are more expensive but in my humble electrician opinion worth the extra cost. Make sure to install the optional clean/flushout valves, they make servicing the units much easier. Installation is pretty simple if you can sweat a little copper or for a little more money use the sharkbite fittings, no sweating. I love these things.
