For decades tankless water heaters haven't been worth the effort to install due to our artificially low cost of natural gas in the USA and the high price of tankless heaters. Tankless water heaters have dropped to under $1,000 while tank water heater prices have continued to climb. Are tankless water heaters worth rethinking?
I have found 3 basic types of tankless water heaters:
1: Non-modulating with battery powered igniter such as they use in Europe. These can be bought in the US for under $230, and use 1/2" gas lines. Most will require an vent upgrade to 4" B-vent. 54 -87% efficiency.
2: Modulating tankless that automatically adjusts the burner output based on temp rise and water flow. They sell for about $550 but must either be mounted outdoors or require very expensive Stainless Steel venting. Most require upgrading gas lines to 3/4". 82% efficiency
3: Condensing that can vent with ordinary PVC pipe, cost just under $1,000. Also requires 3/4" gas line and condensate drain. 95% efficiency.
So I would not ever presume to be expert in engineering, and would be cautious holding myself out as knowing more about that field that I am NOT more than tangentially involved in because I recognize there is more to it than I can get from staying at a holiday in express.
I find all types of professionals think EE and Building Science is something they can speak of as authorities. Architects, home inspectors, HVAC techs, PE's.
But as an engineer don't you hold your work to a higher standard? Any time a change is made to a system, don't you have liability if you don't consider the impact of your change on the whole system? If you don't, then aren't you risking potentially severe unintended consequences that will fall back onto your lap?
If you don't take a band aid approach in your field, why would you recommend people use it in mine? We are not talking about changing a light bulb.
Yes, I do... re-read my comments in the whole blog. It was pro's and con's, plus the need to consider some of the little things that often get over looked.
I also recognize that a solution that works well in one region can be a very poor choice in another region. That may even extend with in the bounds of a city. Some areas of Seattle have gas, some don't... asking gas company to run line for NG so they can install a tankless would be a silly request. Using a tankless in a low electric rate region -- when the heater would be run off of propane would be silly.
Step back and look at the whole picture...
And I am more than tangentially involved in EE and building sciences...
Bob's blog was a specific topic - sometimes you need to focus on the merits of the topic and not try to pull the conversation to far adrift.
FWIW the water heater is in a garage closet next to the furnace. The WH's fresh air supply is fed from the unconditioned air in the attic. A tankless heater could go back in the original location or brought indoors. Bringing indoors would offer a 15' shorter water lines to point of use, but may also use indoor air for combustion depending on the model selected. The current location is subject to infrequent below freezing conditions. The gas manifold is also closer to the indoor location, reducing the cost to run the new gas line.
tankless water heaters are a pretty old idea. They originated in Europe as a way to heat water at the point of use. They were mounted in the kitchen near the sink and the water supply was taken off the one cold water supply line, that at that time was made of lead. Later another heater appeared inside the house (venting into the house) in the one bath room. Again the houses normally had just one water supply line still lead pipe Later one copper line was installed and the wall mounted heaters had a couple of foot of copper pipe from the one supply line.
I haven't seen one installed in Europe since the early 60's.
Its possible thatother regions of the world developed something similar. Anyway it's old obsolete technology.
Steven, last time I was in Germany, nearly every residential house (older than 10 years) was still using tankless. Newer houses were moving over to solar hot water. In the 70's many of the small pension houses had little water heaters that you would turn on and lite before taking a shower or bath. Those have been replaced with the flash electric hot water heaters.
At least two chain hotels that I've stayed at in Berlin were using in bath flash heaters for showers and the sinks. It was just easier for them to upgrade the rooms and push for higher efficiency... without the centralized boilers for all the rooms.
One of the units that Bob listed is made in Puerto Rico.
It really depends on the local energy costs, availability and culture. I can't imagine anyone in their right mind installing a tankless gas or tankless electric hot water heater in Hawaii. I would think carefully about it in Arizona, parts of Southern California, Texas, Florida... they have a good solar insolation and the systems do not need the freeze protection.
China has probably more solar hot water heaters installed than anywhere else in the world... for many it worked better because they don't necessarily have the NG infrastructure - and in some cases the electric infrastructure is also a problem.
But I can also think of cases where it really makes sense. I have a load heat load house... probably under 30,000BTU. Forced air. I could combine an larger Rinnai tankless and their water-to-air AHU to replace my older larger furnace. (house has(is) undergoing deep retrofit). Small gas furnaces are hard to find. I am not fond of the air to air heat pumps for a furnace replacement...
The point is that there are cases where it might make sense and others where it would be inappropriate.
I last worked in Germany in about 1989 and lots of old houses still had them and they served.. but most new houses (1980's) that I saw and stayed in had high efficiency central gas boliers for house heat and hot water. The boilers could heat justwater for showers etc. in the am or pm and there were an increasing number of electric mini tankless in the kitchen.
My mother had a mini electric tankless in her bathroom (on the shower wall)because she took showers at odd times of day.
Apart from those mini electric tankless at the point of service I haven't seen a use for the larger tankless in cooler climates. My knowledge of europe is more the UK and Belgium ... I ought to be more specific.
I now live in Mexico and ... yes I'm 100% solar radiation.
That is probably what I was seeing also. I spent time in mid seventies, late 80's quick trip, then 2000, and later 2010, 2012. The pensioners (B&B) places still seem to use more point of use. In 2012, I saw a lot of solar hot water in places I didn't think it would make sense. In the mid/late 90's Russia cut off the NG supply over disputes with the UK and western Europe (sounds a little familar..) so it may be that some of the construction moved back to point of use for some hot water. I have family and friends that are over across northern and southern Germany... I should ask.
Even if NG is cheap and available in Mexico, I'd still go for solar h20 first. They don't seem to have the price premium for the tanks and materials that we have in the US.