Should I buy a tankless gas water heater?

December 21, 2005 7:19 PM

Anyone have any thoughts on Tankless Water Heaters, specifically gas ones however thoughts on electric ones too would be nice I guess. Distance to kitchen/shower? Ok to put one in a cold room such as a garage? Other important things to know about one before calling the plumber?

For what it is worth, I live with one other person in a house the mild Pacific North West but like the idea of only paying for heating water that I'll actually use rather than just keeping the tank warm.

posted by pwb503 to Home & Garden (24 answers total)

I have other people's thoughts on this... I remember we were talking of such things at my workplace with a bunch of guys who adore talking about their houses and their cars.

The guy who grew up in France did not recomend these water heaters, as he felt they didn't provide enough hot water when needed.
posted by sleslie at 7:34 PM on December 21, 2005

Here's a comparison of some tankless models with flow rates and other attributes. One thing that annoys us about ours (an Aquastar) is that the activation flow rate of 0.5 GPM doesn't permit a trickle of hot water, which we want surprisingly often. We haven't had a problem with having a high enough flow rate though, FWIW. There's no issue with locating it in a cold room, though if it's drafty then pilot lights may be blown out of that's the mode of ignition on your model.
posted by harmfulray at 7:44 PM on December 21, 2005

I had one in a 2 person household a few years ago. Worked great. very efficient.
posted by singingfish at 7:44 PM on December 21, 2005

Using them for a 6 person apartment building. Very very satisfied. With a recirc pump, it means <30 seconds to hot showers in the morning, and after that, <5 seconds for anything else. Fantastic.
posted by sirion at 7:47 PM on December 21, 2005

Ours works fine for a three person household. We can run a shower and the dishwasher at the same time. If I had my time again, I'd put it nearer the bathroom. Sometimes the water takes a while to get to the bath and I fret about the wastage. I'd also locate a/the thermostat there. Make sure you get the volume you need for your needs and make sure you locate it properly. Make sure your plumber knows how to install them. With these caveats, I have no hesitation recommending them.
posted by firstdrop at 8:06 PM on December 21, 2005

Thought you may be interested in this (microwave waterheater)
posted by hortense at 8:30 PM on December 21, 2005

A water heater tank is a good source of clean water in an emergency.
posted by neuron at 8:42 PM on December 21, 2005

We have a Rinnai Infinity 24. We can run both showers and the dishwasher with no worries at all, and it never, ever runs out of hot water. The unit is roughly halfway between the kitched and the master bath on an exterior wall. We get sub-zero (Celcius) temps in Canberra, and even in the middle of winter, there's never more than a few seconds of cold water. It's the best money I've ever spent (the programmable learning Philips remote control is a close second).

I feel like Jean-Luc Picard as I set the Trek-like touchpad thermostat - "Computer - shower, 42oC."
posted by obiwanwasabi at 8:55 PM on December 21, 2005

We really, really wanted a tankless water heater several months ago until we found out what installation would cost! I forget the specifics, but the water heaters were mostly (or perhaps all, by nature of their design) incompatible with our home wattage or whatever (I'm not really that ignorant, just forgetful - I promise :) ). A very experienced and professional electrician came to our house to do some work and I asked his opinion and he was even excited about the idea but then after inspecting our house, realized that just setting our house up to be compatible in terms of electricity would cost thousands, and that we'd be much better off with a new, efficient regular tank water heater. Our house was built in the early 1980's and whoever installed electric obviously wasn't terribly experienced, so that may have some bearing. Good luck to you!
posted by mojabunni at 9:08 PM on December 21, 2005

I've lived in several houses with gas instant water heaters. They work as advertised.
posted by cillit bang at 9:26 PM on December 21, 2005

hmmm... after reading obiwanwasabi's touch pad comment, I guess i used one in korea. As I recall, I had no problems with hot water when showering. When I really think about it, it was actually nice not to run into the "hot water tank running out of hot water" problem that seems to happen when two or more people shower in the same hot water tank household.
posted by sleslie at 10:26 PM on December 21, 2005

Pretty much the standard in China and it is nice to not run out of hot water but I will agree with harmfulray regarding the minimum flow rate. Otherwise great.
posted by geekyguy at 11:40 PM on December 21, 2005

I was reading a bit about tankless water heaters last week. I ran across this article.
posted by well_balanced at 11:51 PM on December 21, 2005

I use what is known in the UK as a 'combi-boiler', which circulates hot water through the central heating system and (separately) provides instant hot water by way of water from the mains being heated through the boiler.

I wouldn't have any other system. I don't have to heat a whole tank of water if I only want a quick shower, and if I do need to use a lot of hot water, it never runs out.
posted by essexjan at 2:19 AM on December 22, 2005

If I had my time again, I'd put it nearer the bathroom.

That is a very good point. No matter what your source of hot water is, the water in the pipe between the source and the outlet is always cold (unless you've just used it), so you have to expel all the cold water from that pipe (and, to an extent, warm the pipe) before you can get hot water out the other end. That wastes a bit of water and fuel (gas or electricity, depending on your system) every time you turn on the hot water.

Put the heater next to the shower or the kitchen sink, or in a spot between the two. If you think you're more a kitchen person than a bathroom person (bigger on dishes than on showers), or vice versa, arrange things accordingly. You might even think about buying two smaller independent systems, one for the kitchen and one for the bathroom, and getting almost no delay between turning the hot water tap and getting hot water.
posted by pracowity at 2:34 AM on December 22, 2005

I had such a gas heater in Germany. It was new when we moved in, and supposedly a good brand. It was okay for awhile, then the problems started.

Repeatedly, the thing would over-heat and shut down! Just like a gas furnace, there is a temperature-sensitive valve that shuts down when too hot. This wasn't due to too much usage. Other times, the thing would blow itself off from starting/stopping. Nothing like getting out of a shower to go, dripping, to the kitchen to re-ignite the heater.

That being said, the things are great, when they work, except for the minimum-flow issue.
posted by Goofyy at 3:19 AM on December 22, 2005

> I had such a gas heater in Germany.

A Junkers, perhaps? They are awful when they are old but great when new and in good condition.

> except for the minimum-flow issue.

Ah. That's also worth mentioning. I didn't notice the "doesn't permit a trickle of hot water" comment above. This bothers me when I want a trickle of warm water to rinse dishes but have to keep the flow higher to keep the heater turned on.

I have seen small wall-mounted electric heaters that trickle just fine (but maybe aren't so great for a hot, high-pressure shower). This is where I think a multi-heater system could be good, with a big beast in the bathroom for showers and baths, and a smaller heater in the kitchen for washing dishes, and minimal space between heating and outlet.
posted by pracowity at 3:54 AM on December 22, 2005

There are a couple of reviews of tankless heaters (Aquastar, Tagaki) at metaefficient.

I've heard about someone in Chicago trying to install one but being unable to find a plumber who was willing to deal with this newfangled technology. You'll probably have an easier time in your area though.
posted by hydrophonic at 6:39 AM on December 22, 2005

I've got an Aquastar 250 from Bosch that I installed myself, and I'm mostly happy with its performance with 2 caveats. First, location is critical. I'm not seeing savings on gas or water since its in the garage (where tank was) and the shower is on the far side of the house. It takes about a minute to get the water there. If I had to do it again, I'd install it closer to where I use it. Second, installing the exhaust stack is important to its function. I initially didn't install the stack (letting it vent into the closet it was in which had a vent up top) and had problems with it overheating and cutting off the pilot after about 5 minutes. Properly putting up the vent allowed more excess heat to escape, and allowed it to run continuously.
posted by TuffAustin at 6:48 AM on December 22, 2005

OK, now I'm thinking about getting one when we replace the furnace... FYI, the minimum flow rate to activate the heater is 0.8 gal/min or 3 l/min, which is about 30 seconds to fill a quart jar (according to the manual). The smaller units require only .5 gal/min, which isn't that much water for washing dishes.

Does anyone know if you can share a horizontal wall vent between a tankless water heater and a high-efficiency furnace?
posted by GuyZero at 7:12 AM on December 22, 2005

My experience from looking into this is that the installation costs are particularly burdensome and not well-disclosed by the people advertising these units. No one can tell you how much it will cost because the building code associated with these things makes every installation unique. $1,000 - $2,000 on top of the unit price is not uncommon.
posted by jbradley at 9:02 AM on December 22, 2005 [1 favorite]

I looked into having this installed in my house for the obvious convenience and the wasteful nature of a hot water heater tank. Both the electrician and the plumber advised that these units weren't the most reliable or useful. Considering the installation cost, we wouldn't have saved much money -- even over several years of use.

I guess both the plumber and electrician could have been lazy, but they were more than happy to recommend other work they thought we needed more urgently.
posted by battlecj at 9:15 AM on December 22, 2005

I've been looking into a tankless as well, and my conclusion:

It'll take so very, very long for the cost savings to pay off that it simply is not worth purchasing.

Here the tankless heaters are running 2x to 3x the price of a top-end tank heater. It would be nigh impossible for the gas savings to pay for the high purchase/installation cost.
posted by five fresh fish at 10:37 AM on December 22, 2005

How about environmental considerations? The U.S. Department of Energy says:

For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters. They can be 8%–14% more energy efficient for homes that use a lot of hot water—around 86 gallons per day. You can achieve even greater energy savings of 27%–50% if you install a demand water heater at each hot water outlet.

posted by pracowity at 11:55 AM on December 22, 2005 [1 favorite]