More interest in tankless water heaters
Well folks – I saw a thread in this area about this subject, but it seemed to go nowhere. The original poster expressed an interest in Propane. At least in my area (Northern WV) propane is very expensive. I’m using propane now and it’s costing me a small fortune. I’m seriously considering changing to a combo of electric and solar and my first purchase is probably going to be a whole-house tankless/instant water heater.
I’ve been doing some research, and talking to various HVAC and plumbing folks, I get quite a variety of opinions. They range from folks that are obviously set in their ways and call the units “worthless” and “a fad”, to folks who seem to be a bit too bleeding edge and recommend going too far to the alternative energy direction.
I tend to like a nearly-scalding shower on a wintertime morinig, since (partially due to the price of propane, and partially due to my menopausal spouse) we keep our thermostat set at 62 degrees.
After a bit of research, here are some things that I’m pretty sure of:
– 50% of fuel for hot water is used for stand-by heat.
– Gas tankless HW heaters require a larger line to boost to the heat needed and therefore might offset the savings from the original HWH.
– Gas HWH companies only advertise 52 degree water with a 40 degree temp rise in their statistics. Adjusting the unit to get a higher ultimate temp will use more fuel.
Anyone else have any input? Have any of you installed these units? It appears that they’ve been used in other countries around the world for some time, but I’m not sure of the hot water usage in those countries. I read an article – written by someone from one of the companies producing electric units – that detailed some of the differences, and electric seems to be the easiest to install and maintain. And also easier to adjust to a higher water temp without costing a fortune.
Any opinions?
Joe H.
The person who says it can’t be done should not interrupt the person doing it. – CHINESE PROVERB
Replies
I have installed two of them, both natural gas units, both in the 199k btu/6 GPM range.
They work well- except for filling a tub. The water is warm, but not "warm enough" for a true hot bath. This can be solved by restricting the flow of water from the tub spout- which results in a longer tub fill time.
Tankless manufacturers provide the temperature rise that the unit will provide at the rated GPM. If your water supply temperature is 40*F in the winter, and the tankless is 77*F rise, that gives a max output temperature of 117*F at the stated flow rate.... which is probaly figured under ideal laboratory conditions. Soooo, once you get the slightest mineral film in the heat exchanger, or the BTU content of your fuel is not the same as what was used to provide the ratings or your fuel piping is off (undersized), you no longer get the maximum temperature rise.
I have a 40 gallon GE 12yr warranty water heater in my house. The EnergyGuide label claims it uses 242 therms of energy annually, and averaged out over a year, a therm of natural gas (100,000 btu- about 100 cubic feet) is roughly $1 here. It costs about $20 a month for the hot water tank to do its thing. If the typical standing pilot water heater is 58% efficient, and the typical tankless is 88% efficient, then I will have a net savings of 30%- which amounts to the grand sum of $4 a month. My water heater costs $388 (new, now) and the comparable tankless is $999, so at a $4 a month savings, I need 153 months (12.75 years) to recoup the $611 difference in equipment costs before installation costs are factored. Applying the $300 tax credit, that comes down to 78 months (6.5 years). Obviously, as energy costs rise, the payback horizon is closer.
I do not know how the govenment establishes the therm ratings. It would be kind of interesting to know what the benchmark is for the usage patterns and water supply temperature involved. Obviously, if you use more hot water, it will cost more.
People that use the "limitless hot water" offered by a tankless will have no energy savings.
Someone suggested an uninsulated 30 or so gallon storage tank piped in series before the water heater. This would allow a "free" preheating of the cold water before it entered the water heater, and it allows more gallons of hot water to be delivered through a standard water heater because the temperature rise is lower.
As far as the whole house electric ones go, I hope you have a electrical substation in your back yard. It won't be maintenance free, either. Better price out the contactors in there, and keep one or two handy.
I think the most energy efficient setup with conventional fossil fuels is a small condensing boiler and an indirect fired water heater. Not for the faint of wallet- especially if you do not have radiant heat or an air handler with a hot water coil. Those boilers can be well over 90% efficient, and coupled to a well insulated 100 gallon storage tank, there is no reasonable shortage of hot water.
The cheapest way for anyone to lower their hot water energy costs is to change your usage habits. People don't like to hear that, though.
Thanks for your response. Understood on changing one's water using habits. Our issue is, we think we're fairly efficient now. There's only two of us, we don't take long showers or sit in a tub for hours (how can anyone do that anyway?) - we do run a dishwasher, but only about three times a week. We have a propane-fired forced-air furnace, water heater, and a dual-fuel kitchen stove. Our house is around 2100 SF and reasonably well insulated, but our propane bill is still $240 per month, year-round. Last year it was $275 p/m. Back around 2001 or so, we had a really cold December, and propane costs were going up as fast as gasoline is now - we had a gas bill of over $900 for one month! The folks in our little area have been told by the local gas company that they will never run natural gas lines into here unless we pay for it ourselves. The last estimate we got for that was so high that it was out-of-the-question, so we don't have many options. Whether or not the water heater pans out to be more efficient and cheaper, I'm giving serious consideration to removing my furnace and switching to electric baseboard heat. It's popular around here, and seems to be cheaper to operate. We have no need for A/C, so except for patching the ductwork holes in the floors and walls the rest will be relatively easy to install (except for a second electric panel).
The person who says it
can't be done should not interrupt the person doing it. - CHINESE
PROVERB
Electricity is a great option- as long as it remains "cheap" in comparison to the other options.
Ethanol was relatively cheap, until more people got on the bandwagon and increased demand. Now the prices are going up. Placing all of your energy needs in the electric basket may not be the best choice.
Unless your home has 2x6 exterior walls insulated with something other than fiberglass batts, I would not consider it "reasonably well insulated". Infiltration is just as important as the R-value, and fiberglass does little to address that issue. Another example of a few more dollars upfront having payback for the life of the structure. My home, built in 1967/68 only has R-9 fiberglass in the walls, and the only way to fix it is to move or tear off the interior drywall and redo it.
Tearing off drywall on exterior walls and reinsulating and then replacing the drywall is a cheaper option than a high zoot HVAC system in search of efficiency and comfort.
Forced air heat is reasonably inexpensive to install compared to hydronic heat, but it costs more than hydronic to operate.
If natural gas is not an option, then maybe you should seriously consider a ground source heat pump- which is much more efficient than an air source heat pump. Especially if you plan on staying there, and if your area supports the technology.
A R-410A heat pump will give a hotter discharge temperature in the heating mode, but unless you spend the money on a variable speed drive air handler, the operating costs will get out of sight when the unit operates constantly closer to 20 degrees and below. You will also have to find the best balance between a condenser large enough to heat without going into the resistance backup.
Hey Dan you might want to look into this insul retro option. Can be pumped against existing FG. There is a video on the site that shows this.http://www.retrofoam.com
interesting stuff...
Wegotrocks: Igotrockstoo! We put in a SEISCO electric tankless and have been using it for 4 yrs, now. It's a BIIIIIG sucker - 28KW peak electric demand. We absolutely love it!!!! Cost a bundle - about $600. But still worth it. We have the shower installed directly above the dishwasher & have run them at the same time. You want scalding, you can get it. Our heater will put out more hot water at a temp you cannot stand under w/ the dishwasher going. Would fill a swimming pool if you wanted to. Greatest thing since Easter Subday afternoon Braves Baseball (Which my wife is snoring through & I am ignoring, typing this to you.)
Now, to tell you the whole story. Remember those Mickey Rooney prison movies where they tested "The Chair" & the lights dimmed? We have 200 Amp service. Our lights momentarily dim when that current sink turns on & acts as a near short circuit across both legs of our service. It lasts but a few seconds, & now we do not notice it without thinking about it. If I understand it completely, it sucks full rated current when it starts up, then as it establishes hot water out of its owm outlet, starts throttling back to what is necessary for the demand. It has a humongous circuit board in it w/ all manner of logic/control ckts. We also have it feeding a 1" main supply line so we don't have a problem w/ supply at the using end of the pipe. It's about a 65 ft run to the shower/dishwasher tee.
A word of warning - our first one detonated one night at about 2 AM. Seems we had a fitting on the wall about 5 ft above the heater - sprung a very slow leak going drip - drip - drip for several weeks, we discovered. Water got into the WH & shorted out a 220 V ckt that blew its top. SEISCO sent me a new WH the next day at a very good price, considering that it wasn't their fault & it was out of warranty, anyway. Point - don't put anything above the WH that can leak.
You find them on line by Googling on "SEISCO." They are in Houston, TX, but may have a dealer/distributor in your neck of the woods.
Do we like it, you ask? Well enough to buy a second one for our glass studio. Just as big as the one in our house. We live way out in the woods in Nawth Jawja (Honeychile) & have no natural gas. Propane is likewise extremely exoensive. Electric is the way to go for us, also. Have any specific questions - send 'em in. Be glad to answer them.
Don Reinhard
The Glass Masterworks
"If it scratches, I etch it!"
Thanks for the reply Don. I've check on the Seisco unit, and of all the ones that I've been looking at, it seems to be the on with the most potential.Do you have any data on your electric bill before and after installation? How bad is the dimming effect when the unit comes on? Do you have many high-techy toys/equipment (stereo, computer, etc.) and how does it effect them. I'm wondering if the power valleys and spikes would eventually degrade computer hardware.I'm a property inspector, and for a period, I was doing draw inspections for a contractor around here. He was telling me that he has a completely electric house just slightly smaller in square feet than ours, and he's paying around $140 per month for electric, and that's his only utility bill! He also has a forced-air furnace with an electric heat exchanger - not many of those around.I'm considering an electric heat pump as well as electric baseboard as some of the options.Joe H.
The person who says it
can't be done should not interrupt the person doing it. - CHINESE
PROVERB
Granite chunks: OK - here's the poop on our house. New in 2003. Moved in Labor Day weekend that year. Seisco unit installed at that time. We are in the north woods of Nawth Jawja (Honeychile) far, far away from natural gas. Electricity is from a rural electric Co-op, so it isn't cheap. We are one of only 8 customers on our main Ckt. When we moved in, we were one of only two. Rather desolate. We have underground service from the power company lines to our house. Cost as much to install as power poles & much more reliable in event of ice storms & hurricane. $1800. We built a super insulated house, about 1800 Sq Ft. Used insulated concrete forms for lower walls, 2X6 for upper story & had foamed in place urethane installed for insulation. Have attic insulated, also, so AC ducts are in insulated space. Had 96% effecient dual fuel heat pump installed for heating/cooling. Switches from electric to Propane at about 32 degrees. Propane is fairly expensive, so we bought our own 500 gal tank & look for cheapest gas of year & fil up then. That usually turns out to be August. A full tank lasts us at least two years. We have recessed can lighting in all rooms, using 75 watt spot/floods. Have also installed electronic Lutron dimmers. We did not spare the number of light bulbs, but have zoned the bulbs on multiple switches so we don't have to turn on more than we need. F'rinstance, 22X25 LR is zoned w/ 4 switches. We have an electric range & oven. My wife's hand doesn't move downward, so she cannot turn off lights. We leave a few sections of lights on at night at a low level so we can see if we have to get up for any reason. Also have an electric clothes dryer. Also two fridges & two freezers. Don't get to the store very often, so we need a fair amount of temp controlled storage. Pump house is 200 plus feet away from house; pump is at over 375 feet down, requiring a pretty big pump.OK - now you know that we live somewhere between Al Gore & the rest of the world. Our monthly electric bill is about $140 average for the year. Not too shabby, considering that includes heating/cooling.We have 200 amp service w/ a full 40 position main service box. Lots of individual ckts. The WH uses 4 X 50 Amp Ckt Brkrs. It uses nowhere near that much current when the WH kicks in. The IR drop between the Main panel & the WH is not very high - it is only a 4 ft run from Main to WH, using appropriate size wire. How much do the lights dim, you ask. Not enough to notice unless you are thinking about it. When we first started using it, I was looking to see if the lights dimmed - yup! MOF, I commented to my wife about testing the chair for Killer Mears. She looked at me like I had lobsters crawling out of my ears! We do not even notice it now, unless we are looking directly at the lights when we open the kitchen faucet wide open. It is momentary.We have two very large TV sets along w/ all the usual other electronic crap that goes along w/ modern living. Does it affect them? No. Never noticed it. I think they can operate at a much lower voltage than we have with the drop due to the WH coming on. We also have a computer on a UPS (The only way to go in the wilderness). The UPS never kicks in when the WH comes on. The UPS kicks in more times for low power company voltage. I hear the relays clicking down there very frequently & the WH I know isn't coming on. We used to have the same problems w/ low voltage when we lived in metro Atlanta. I always heard the UPS clicking in. One TV set has been operating here for over 6 yrs. The other for three. The one in the Bedroom often is on 24 hrs a day to provide background noise at night. I think that indicates that we have no appreciable degradation from low voltage.My electrician had a cow when he installed the cables for the WH. As I recall, I went one size larger than code required. WE have a lot of electric equipment, & have no problems w/ any of it. Needless to say, everything isn't on at once. Sometime in the future we will install a heat exchanger - forgot that little item. Hope I've covered everything. More questions, ask.DonDon Reinhard
The Glass Masterworks
"If it scratches, I etch it!"
Wegotrocks,
I don't think you are correct in standby losses on a modern gas water heater. With the new energy efficiency standards, I would bet that the standby losses are no more than 20% of the total energy used in a typical house. Of course, if you use less hot water, the percentage of the standby losses increases but in any case, with natural gas, the standby costs about $.25 per day.
In general, using national average fuel costs, it costs three times as much to heat water with electricity than it does with natural gas even though electric water heaters are much more efficient. I do not know the heat content and cost comparision between natural gas and propane but that should be pretty easy to compare....cost per Therm. Unless propane is much more expensive per Therm than natural gas, it is very unlikely that it is wise to convert to electric.
Bill
wegotrocks,
I have had a Takagi TK-Jr installed for the last 6 months (nat. gas). It is a smaller unit (one shower at a time). I live alone, thus no problem with volume. There are some quirks to tankless, though. I had to resize the gas line to 3/4". Also, the venting can be prohibitively expensive. The Takagi requires Category III vent pipe, stainless steel and very expensive ($200 to go up 5ft.). The Bosch may be using type B vent pipe and of course the electric, none. They don't fire up instantly; after sensing water flow, there is about a six second delay until hot water flows. Add this to the amount of time you wait for hot water to reach each fixture. Also, there is something called sandwich effect - if you turn the water in the shower off to soap up, then turn it on again to rinse, that six second delay allows about six seconds of cold water flow into the pipes when you turn the faucet back on. Despite all this, I am quite happy with my tankless. I really like the fact that it just sits there and does nothing except for the three minutes each day that I use hot water. The electricity that it uses in standby mode is so low, I watched my kwh meter one day when nothing else in the house was on and could'nt tell if it was moving or not.
We put in a natural gas Noritz that just serves two bathrooms. The existing tank WH is about as far away as you can get, so when we added on we got the tankless. It's mounted outside, which does away with the vent issue, but we did upsize the gas line.
Having it close to point of use to reduce water use while waiting was the main thing for us. It's set at 105F, which seems to be fine for getting as hot a shower as I'd like. The issue we had last summer was that, when set higher, the hot water flow would drop enough to cut off the burner.
We installed a Takagi TK-1 about 6 years ago and noticed a pretty good nat. gas savings right off (close to 45%), but kids and baths soon followed so no time to keep track of that stuff anymore. Our water supply is surface water, so northeast winters made it a bit tough for it to heat up the tub water enough until I restricted flow, the ow-flow shower head never had a problem with keeping hot. Takes about 6-7 minutes to fill tub now, just enuf time for me to catch the youngins and git'em naked for the bath. Ditto on the extra seconds to warm up water, especially noticable when you want more hot water after shutting it off for a few (6) seconds... but we've easily adjusted.