Electric tankless water heater

[CREATIVE1]

I've been reading blogs until I'm crosseyed.  There seems to be a generally negative impression of electric tankless water heaters.  Comments please?

[John_C]

My spin on electric tankless water heaters.

Scenario 1
One or two water frugal people live in an area where the temperature of the incoming water is moderate.  The layout of the house is such that all the hot water outlets are relatively close together and close to where the water heater would be, which is a short run to the main breaker panel. Very modest electric costs.

Scenario 2
A family of 4 or 5 in a house with 2-1/2 baths, hot water fixtures far apart.  No particularly good central location for the water heater and very cold incoming water temps for several months of the year. Above average elec. costs.

The folks in scenario 1 would likely be happy with a centrally located electric tankless water heater.

The folks in scenario 2 would probably not be well served with such a system.  The electric systems have lower BTU output than NG or LPG systems.  Someone turning on a fixture in a different part of the house from a running shower would likely cause the hot water temp to drop significantly, especially if the incoming water was very cold.  The lower cost of purchasing the unit would be offset by the high cost of heavy gauge wire and high elec. costs.  They might be ok with a few point of use water heaters ...  better with some energy source other than electric.

As always there are ways of mitigating the problems. I have an acquaintance who has a 1000 gal water tank in his basement not too far from the furnace. The water going to the heater is pretty much 60º year round.  The bathrooms on the second floor share a wall and are  are stacked directly above the kitchen-laundry-bathroom on the first floor.  The water heater is in the laundry about 8' above the electric panel in the basement.  They are very happy with the system.  It wasn't designed around the electric tankless water heater ...  but it might as well have been.

[CREATIVE1]

There are two of us, and the distance between kitchen/laundry/bathroom 1/bathroom 2 is minimal.  I'm guessing probably ten feet from bathroom 1 to laundry, 6 feet from laundry to kitchen sink, 12 feet from kitchen sink to upstairs 1/2 bath (including vertical run between floors).  The heater would go in the laundry.

I've also seen posts suggesting a small water heater, maybe ten gallons, in addition to the tankless heaters to even out the heat. ?
Several bloggers did that to fix uneven temp problems and were happy with the solution. 

[John_C]

I've also seen posts suggesting a small water heater, maybe ten gallons, in addition to the tankless heaters to even out the heat.

I don't get that.  You would quickly use that water up and be back to square 1.  I've seen systems with a normal to largish conventional water heater with the temperature set very low.  The idea is to make sure the water going into the tankless heater is not very cold.  A standard water heater set at 80º (if you can set it that low) would use very little elec.   An electric tankless water heater would put out a lot of hot water if the incoming water was that warm.  20  or  30  gal water heaters are not much more expensive than 10 gal heaters.

Either way is really doing what the 1000 gal tank in the above post accomplishes.  He put that tank in when he bought the house because the well was a couple hundred feet down the mountain.  The second tank - pump helped even out some water pressure issues the previous owner complained about.  The general improvement in water heating efficiency was an unplanned benefit.

My own very limited experiments have been that a timer on the water heater cuts the elec use significantly. I don't know where you live so it's hard to make specific recommendations, but if I was designing a system for myself in N GA I'd plan on an inexpensive bread box solar water heater with an LPG tankless as backup. I'd drain the bread box heater during the roughly two months when a hard freeze is possible.

[cordwood]

 To keep from running 40 feet of pipe from the main water heater to just the kitchen sink I installed a "Tiny Titan" 2.6 gal. electric under the sink,.....seemed like a good idea at the time but after using it for about three years now I wish we would have gone with a 5 gal. one.
All the tankless ones I have been around were gas and I was less than impressed with them as well. To just heat water enough to wash your hands and face in a work shop they worked good but anything like washing dishes where you want HOT water they were inadequate. JMHO

[glenn kangiser]

A decent sized electric tankless water heater will double the size of your required electric service.  They can take as much or even way more than it takes  to run your whole house.  In the PNW at least you have cheaper electricity.

We have the Bosch Aquastar HX125 - a discontinued model, but there is an upgraded one to replace it.  It works on propane and supplies all of the hot water we need.  We only set it to heat as hot as the hottest thing we want to heat.  That would be just under scalding in the shower. 

The reason is is you set them near boiling they will scale inside and possibly destroy them sooner than they should.  Without them ever getting to boiling scale doesn't build up.  There is no need for super hot water if you have all of it you need.  It could still be set above scalding if you wanted it extremely hot without scale as it is still well below boiling.

Ours will serve two outlets at once - say shower and wash machine if needed.  We are happy with ours.  Off grid you never use resistance items such as heater coils unless you are trying to burn off excess power that would overcharge batteries such as from a wind generator which can not be unloaded so output must be used.  Exceptions would be short term use items such as a toaster, hair dryer etc.  No room heater or water heaters.

[CREATIVE1]

So a 200 amp service won't do it?  Also, we're having the buy our transformer and went with the smaller model, 15 KV.  Sounds like a problem here.  

More info: we have a well that pumps uphill to a 1000 gallon plastic tank so the water is gravity fed, right now through a big sand filter before it goes to the trailers.  We could cut out the tank when we build the house and hook up to electric, or maybe do something else with it closer to the house. Underneath the house probably won't work--2 foot perimeter foundation.  Gets down to the 20's in the winter, by the way.

[glenn kangiser]

Here is one of the more common electric ones.

It looks like up there in the cold it will use at least 120 to 150 amps to keep up with something you want hot like a washing machine.  The 200 amp service could do it as the rest of the house would likely get by on the 50 amps left.

http://www.gotankless.com/products.html



This looks like interesting info - I didn't read it all.

http://www.tanklesswaterheaterguide.com/

[cordwood]

A decent sized electric tankless water heater will double the size of your required electric service.  They can take as much or even way more than it takes  to run your whole house.  In the PNW at least you have cheaper electricity.

We have the Bosch Aquastar HX125 - a discontinued model, but there is an upgraded one to replace it.  It works on propane and supplies all of the hot water we need.  We only set it to heat as hot as the hottest thing we want to heat.  That would be just under scalding in the shower. 

The reason is is you set them near boiling they will scale inside and possibly destroy them sooner than they should.  Without them ever getting to boiling scale doesn't build up.  There is no need for super hot water if you have all of it you need.  It could still be set above scalding if you wanted it extremely hot without scale as it is still well below boiling.

Ours will serve two outlets at once - say shower and wash machine if needed.  We are happy with ours.  Off grid you never use resistance items such as heater coils unless you are trying to burn off excess power that would overcharge batteries such as from a wind generator which can not be unloaded so output must be used.  Exceptions would be short term use items such as a toaster, hair dryer etc.  No room heater or water heaters.

The ones I dealt with at ProFlame were Rinnai (don't recall exact model) but if you had any fluctuation in water pressure at all they were bad for going hot/cold/hot/cold and in the shower that ain't .  Is your water pressure more stable or is your unit that much better at maintaining temperature? This was also many years ago so they may be better now

[CREATIVE1]

Water pressure should be stable.  That's a new take on why water temperature fluctuates in the shower, something noted often on the internet.   As you say, NOT COOL.

[harry51]

I put a small Stiebel-Eltron electric tankless (model DHC8, IIRC) under my multi-purpose sink in my shop. It called for a 40 amp breaker and AWG8 wire. It makes plenty of super hot water for hand washing, dishes, etc.

http://www.stiebel-eltron-usa.com/dhc.html

The main drawback for me is that it requires a bit more than 1/2 gal/min flow to activate it. That sometimes forces us to use more water than is really necessary, just to get the water heater to kick in. We pump all our water periodically from our spring tank up to our storage tank, and it's gravity feed from there to point of use, so we don't like to waste it.

On the upside, it's compact, easy to install, makes plenty of hot water, and didn't cost much to buy. I can't comment on the effect on the power bill because of the limited use in our case.

[glenn kangiser]

A decent sized electric tankless water heater will double the size of your required electric service.  They can take as much or even way more than it takes  to run your whole house.  In the PNW at least you have cheaper electricity.

We have the Bosch Aquastar HX125 - a discontinued model, but there is an upgraded one to replace it.  It works on propane and supplies all of the hot water we need.  We only set it to heat as hot as the hottest thing we want to heat.  That would be just under scalding in the shower. 

The reason is is you set them near boiling they will scale inside and possibly destroy them sooner than they should.  Without them ever getting to boiling scale doesn't build up.  There is no need for super hot water if you have all of it you need.  It could still be set above scalding if you wanted it extremely hot without scale as it is still well below boiling.

Ours will serve two outlets at once - say shower and wash machine if needed.  We are happy with ours.  Off grid you never use resistance items such as heater coils unless you are trying to burn off excess power that would overcharge batteries such as from a wind generator which can not be unloaded so output must be used.  Exceptions would be short term use items such as a toaster, hair dryer etc.  No room heater or water heaters.

The ones I dealt with at ProFlame were Rinnai (don't recall exact model) but if you had any fluctuation in water pressure at all they were bad for going hot/cold/hot/cold and in the shower that ain't .  Is your water pressure more stable or is your unit that much better at maintaining temperature? This was also many years ago so they may be better now

My pressure is very stable as I pump up to a storage tank about 80 feet elevation above the house then gravity back down so it's a pretty even 30 or so PSI. 

[Jens]

I have heard that you might as well have a seperate 200A service installed just for the water heater.  check into solar water heaters, and get a regular tank style to suplement is my suggestion, if gas isn't a possibility.

[CREATIVE1]

It sounds like that's a good idea.  I am looking at some solar sites too.

[Jens]

I think it was mother earth news that had an article a few months ago on batch style solar water heaters.  It uses a minimum of new materials, and so, is inexpensive.  They currently have a magazine (Mother earth news) that is all about alternative energy, just saw it at the co-op.  It has an article in it too.  here is a good one too.
http://www.instructables.com/id/Solar_Hot_Water_Pre_heater/

cheap!  once we can get around to it, we are going to do one by the garage with a few old water heater tanks.  That is ofcourse, after the house, after the chicken coop, after the garage, etc, etc.  Maybe I can squeeze it in between there somewhere without subjecting myself to the wrath of DW

[CREATIVE1]

Cheap is for me.  If inspectors weren't buzzing about this would be a whole different kind of project. 

[Jochen]

I have the Stiebel Eltron Tempra 24 in my home. And I love it. I really can't understand why everybody here in the USA and Canada is still buying the "old style" water heaters.    Natural Resources Canada is estimating that up to 33% of the electricity bills in residential housing is caused by these old fashioned type of water heaters. Or why the heck can't you get here a decent washing machine with a built in heating system. I priced one her in Canada and it was over C $2,000.- plus Tax.  In Europe nothing else is on the market and they are cheap as well.

Jochen

[CREATIVE1]

Well, there's always a timer.  They help.

[MountainDon]

....fluctuation in water pressure at all they were bad for going hot/cold/hot/cold and in the shower that ain't .  Is your water pressure more stable or is your unit that much better at maintaining temperature? This was also many years ago so they may be better now

I could be wrong on this, but I think that now all shower controls are equipped with pressure compensating devices. The ones I've seen that are not compensated are marked "not for new installations, replacements only" or words to that effect.

I installed a pressure compensating shower control about 15 years ago when I remodeled our master bathroom. At the time they were uncommon and extra expensive, but they are wonderful... no change in temperature when the toilets flush, etc.

[cordwood]

....fluctuation in water pressure at all they were bad for going hot/cold/hot/cold and in the shower that ain't .  Is your water pressure more stable or is your unit that much better at maintaining temperature? This was also many years ago so they may be better now

I could be wrong on this, but I think that now all shower controls are equipped with pressure compensating devices. The ones I've seen that are not compensated are marked "not for new installations, replacements only" or words to that effect.

I installed a pressure compensating shower control about 15 years ago when I remodeled our master bathroom. At the time they were uncommon and extra expensive, but they are wonderful... no change in temperature when the toilets flush, etc.

Since this thread I have researched a little more and have concluded that the tankless I was using was cycling on and off because of to little flow through the unit, California pushed them "low Flow" shower heads on us!
Some of the reading I have done would lead me to believe that a compensating valve could lead to the same problem.
Most of the good things I have read were when the house was plumbed for the unit and NO water saving devices are used, Not a big fan of that
I am still looking into them for the new house but with their high price I sure want to be certain it works right. and anything that requires a 3/4" gas line must have big appetite for some fossil fuels I kinda want to down size my footprint not make it bigger

[MikeT]

I have explored this as well.  Same house plans as CREATIVE1, same general region (Pacific NW), and the same desire for value.  I decided against the tankless except for a small water heater for cups of tea, etc in the kitchen sink.  I was also looking at the Marathon water heaters because the local PUD is giving rebates on the purchase of these very energy efficient tanks.  But the more I think about it (especially since I will not always be there except on weekends, vacations, etc), I will go with the old standard electric tank and try to get the best deal I can.  I may even try and get a dinged new one off Craigslist.

mt

[glenn kangiser]

We have the low flow heads etc. on everything and our tankless works fine but is very touchy on adjusting to lower heat.  I found setting it too low caused it to shut off too oon o we are set just below scalding and working pretty well.  We like it.

[MountainDon]

I believe there is a bit of a balancing act between tankless heater temperature setting and low flow showers.

It is also possible to have the tankless set to too high a temperature for the flow. Picture an extremely low flow head (1.5 GPM), coupled to a heater set at a very high temperature. At the shower you set the temperature somewhat low, and that can cause the hot water flow rate to fall below that to actuate the burner/element.

[wildbil]

I believe the choice of tankless water heaters vs normal water heaters comes down to a few questions.

Do you care about water conservation? or are you worried about energy conservation?

tankless require the water to be run through them before they kick in, tanks require constant energy to keep the water warm.

I have come to the conclusion that a happy medium would be a small tank water heater. less energy to keep warm than the normal sized ones, and less water usage cause the water gets colder quicker.

But if you arent worried about either of the above questions then the questions are about money and space.

sorry if i ran off track on this topic.

Wildbil

[CREATIVE1]

Not off track at all.

I'd like to save energy, money, and water, not necessarily in that order.  Any ideas are helpful.  I'm also considering dual flush toilets, rain barrels, and many other interesting options to accomplish some savings. 

In Tampa, I'm still using a 30 year old solar water heater that came with a system I won at the fair (!!!!)  The solar panels are long gone, but along with a timer that heater works great.  I need a bigger tank because of the soaking tub almost next to it.  My biggest luxury, and one to be repeated in our new home.