apartment therapy changing the world, one room at a time

We had a tankless water heater in my apartment in Japan (masters of small living), and it was totally awesome.

As with every article on tankless I've seen, there's a lot left out. Firstly, the heading---50 scalding gallons--makes for a good image, but in reality, with current levels of insulation, the heat/energy loss from the tank is small (not negligible, but not high.) With electric heaters which don't have a flue, it's even smaller.

Tankless heaters are expensive to buy and expensive to install, since a whole-house heater needs a dedicated extra gas line. All tankless heaters start up slow and take 15-20 seconds to really produce hot water, not a big thing in itself, but they also require a continuus flow, typically 3/4 gal a minute or they shut off, making rinsing dishes the way I do, in a trickle of water, impossible. Or shaving.

There's also concern that they "lime" up with deposits so their life may be only 6-10 years.

Finally, in actual tests, the savings is typically 10-15%, not bad, mind you, but far less than the image being touted. I computed that, in NYC with a summer gas bill of $90 or so, I would save less than $10/month.

Chandru,

Your concerns bring up a good point: technologies like this, which assume a change of behavior (i.e., the water will always be on full force), don't always work in the real world.

While it's true that lots of energy conservation measures do not pay for themselves, the idea is that if everyone saved a little bit it would add up to a lot.

This is the most common hot water heater in France and one that my family has had installed here in the states for a long time. It's a great space saver, it can heat up HOT, way warmer than I would ever have my regular water heater set all the time.

We did have a problem with it shutting off if it wasn't running enough warm water through, but got it adjusted so that now it's constant. However, getting rid of a perfectly good water heater can be a waste and I would only change over to the on-demand my current water heater conked out on me. For what it's worth.

Regional differences: my first thought was, "You have to let it run full-force to heat up? But that's wasting water!"

I have a gas on-demand heater in France - great things. It's true that it doesn't get going if you start with the hot tap in trickle mode. However, you only need to have the water going full-force for a second to get the gas burners up and running and then you can really reduce the pressure and still enjoy lovely hot water. As Laure mentioned, adjusting the water temperature also means the burners need a lot less water pressure to get started.

Re: the warning on electric models in the text above. I need to replace my hot water heater and have been considering a tankless, esp given the rebate. But since my system is electric with no option for gas, will this be a terrible choice?

I have two ELECTRIC tankless hot water heaters in my house- one for each "wing." Some observations:

-The hot water is virtually instantaneous, and yes, it is impacted by the pipe length between the point of use and the heater. However, contrary to popular myth, the water gets very hot and it works well with showers.

-I have one hanging on my laundry room wall and one hanging high up in my master bedroom/bathroom closet. It requires no ventilation.

-It does make an audible clicking noise, which tells you that the hot water has been engaged.

-My heaters have stepped circuits that minimize energy use by coming on in stages (depending upon water demand), as opposed to always firing up 100% when engaged.

-Electric water heaters require IMMENSE electrical capacity. I had to have a dedicated 90-amp circuit added to my existing 200-amp service. Accordingly, the price of installation is pretty high. In addition, your plumber and your electrician will have to work together, which is not as easy as it sounds.

Hejiranyc, could you let me know the manufacturer and model of your heaters? I'd love to research them for a future post. Thanks!

My previous apartment had an instantaneous hot water heater and I LOVED it! It fit in the kitchen cabinet and provided very hot water very quickly for both the kitchen and bathroom. I miss it every day.

Now I have an electric hot water heater (tank style) that I find absolutely useless. It holds a very small amount of water which only allows for about a 6 minute shower (with very low water pressure). Sure it helps us save water, but only one of us can take a shower in the morning, so I end up taking my showers at night. We don't have gas in the house yet (next year hopefully), but when we do, the first gas appliance I will install will be an instantaneous hot water heater!

P.S. Hejiranyc, 290A of power is a LOT for a house, but not having gas would greatly increase your power demand, particularly for functions like heating the house, and heating water. Gas (if it is available) is a far more efficient, greener (depending on the source of electricity), and less expensive option.

I have been thinking about these in my next remodel but based on the comments here, and similar comments regarding functionality and cost from other sources, it sounds as if the tankless waterheater will not be a part of this remodel.

What about some information on how to put your hot water tank on a timer? Currently, it keeps the water hot all the time. Is there some way to use less energy by changing the heat setting automatically at the times of day when you know you aren't going to be using hot water? Sure, I can go turn it down before vacations or even when I leave for work every day, but isn't there something more practical?

hejiranyc - so, given how much the installation cost, how long do you figure that the tankless units took (or are taking) to pay for themselves?

In the winter, isn't the heat loss of a conventional hot water heater just contributing to the heating of the dwelling (so it's not a total loss)?

Good question, Pixie. It sounds like both gas and electric tankless water heaters will require running new gas/electric lines and water lines. That work alone could equal the cost of a new conventional water heater. Money is tight these days!

Jon_B - that's true that the water heater warms up my place in the winter, but it also warms it up in the hot DC summers a lot, resulting in more air conditioning. The water heater is in the bedroom closet and in the hot months, the bedroom is a lot warmer than the other rooms.

I replaced a 50 gallon hot water tank that was the sole hot water heater for a 3 flat apartment building in chicago, (3 bathrooms in all) with a single Rinnai tankless unit, and I am pretty happy with it.

It required no special gas line (using the same supply as the furnace, which it's next to) and takes up much less space. It did need to be vented directly to the exterior.

It heats the water perfectly, even in the dead of winter (when the incoming chicago water is ice cold) and have had no complaints from my tenants. It won't rust out and flood the groundfloor apartment, and I like that it's not running when it's not being used. It's incredibly quiet.

The main difference in usage is caused by the distance from the end use. Because it's two floors below my unit, there is a lag from the time you turn on the tap to when you start getting hot water ... and this distance exacerbates the effects of the heater if you are turning the water off and on repeatedly.

Sadly, it's also been hard for me to tell exactly how much gas is being saved. My buildings furnace and hot water heater are on one line, and variations in use of both hotwater and heating month-to-month over the 18 months we have had it make it difficult to see a pattern.

But this months bill says we used an average 13.22 therms of gas per day, vs. 15.00 in the same month last year - with this march being one degree colder on average, than last year..

Basically, I love it, though ideally it would be installed as close as possible to the primary end use (shower.) Seems like it would be ideal in an apartment / condo setting where it replaces an in-unit tank, though that is not my situation ...