EVIL electric tankless hot water heaters

rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
I really should install a solar water system, but I really hate plumbing stuff.
I have a small one bedroom house. Natural gas source is 100 feet away, I'd rather avoid making a trench and running a gas pipe out there.
I can get a name brand electric tankless hotwater heater for $300 used on ebay.
I can get used solar hot water panels 4x8 for $150 on craigslist. It has been this way for years. I have no idea why there are always so many available, but there are.

but a drain back system is another $1000. or I could just do a hack system with a freeze protection valve and shut it off in November and start it up in March in South Carolina. that would save me the $1000.

the problem I have with hot water solar is I still need a back up system right? so I might as well get the back up electric tankless right?
I pay about 11 cents a kwh, any reason why I should not get a tankless electric heater and hope to add solar hot water panels latter?
thsi will be a rental property, I don't really want to invest a lot in it. I have just read a LOT of bad reviews on electric hot water tankless systems. House would be on well water 10grain hardness. so I guess I will have to vinegar purge it once a year or more often.

Comments

  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters

    Used to work for a company that among other things, sold tankless hot water to customers who really wanted them. I don't know anyone who was really happy with them. And cost? Don't forget the major electricity supply and related wiring they demand. That alone could cost you a bundle and could even require upgrading the electrical entrance. Not cheap that. And vinegar may not do the job either, you may have to use a strong acid.
    In my opinion far better to get a small conventional electric water heater and add lots of extra insulation. And a lot cheaper too.
  • jonrjonr Solar Expert Posts: 1,384 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters

    The people I know that are really happy with electric tankless live where it's very warm and the water needs very little heat. Tankless propane couldn't turn down far enough and a propane tank heater is wasteful (due to heat loss from the tank).

    A heat pump water heater would be more energy efficient than electric tankless.

    I am available for custom hardware/firmware development

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: EVIL electric tankless hot water heaters

    Do not buy an electric tankless heater.
    Just look at the specifications to see why.
    Hint: you may have to upgrade your service to power the thing.
  • BB.BB. Super Moderators, Administrators Posts: 31,433 admin
    Re: EVIL electric tankless hot water heaters

    Plus, from what I have read years ago, people complain that their home lights keep "blinking" because of the heavy load/constant cycling of the tankless heating elements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: EVIL electric tankless hot water heaters

    We quit doing solar DHW because of its unreliability. Solar electric has come down in price so much that I recommend keeping the simple, cheap electric water heater and up size your solar GT. And that way, when your water heater is hot, the solar power can go for other uses.
  • BB.BB. Super Moderators, Administrators Posts: 31,433 admin
    Re: EVIL electric tankless hot water heaters

    The installer for my system (10+ years ago) stopped doing thermal installs--He is an electrician and the solar hot water was just too much of a nightmare for him to stay in that side of the business.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: EVIL electric tankless hot water heaters

    "A heat pump water heater would be more energy efficient than electric tankless. "

    really? what data backs this up? I am finding a hard time finding how much money one would save when comparing
    traditional electric hot water tank
    vs tankless
    vs heat pump tank
    any research done on this?

    the Tempra 20 tankless heater i am considering uses two 50 amp breakers, and I have tons of room in my breaker panel box.
    if I can save a lot of money doing the heat pump tank I'll do that,
    I really hate the ineffciencies of a traditional hot water electric tank so I probably wont' go that route.
  • BB.BB. Super Moderators, Administrators Posts: 31,433 admin
    Re: EVIL electric tankless hot water heaters
    "A heat pump water heater would be more energy efficient than electric tankless. "

    really? what data backs this up? I am finding a hard time finding how much money one would save when comparing
    traditional electric hot water tank
    vs tankless
    vs heat pump tank
    any research done on this?

    the Tempra 20 tankless heater i am considering uses two 50 amp breakers, and I have tons of room in my breaker panel box.
    if I can save a lot of money doing the heat pump tank I'll do that,
    I really hate the ineffciencies of a traditional hot water electric tank so I probably wont' go that route.

    A tankless electric heater vs tanked electric heater--The difference in losses is the heat loss in the tanked heater insulation. Add more insulation and get less losses. Both convert 100% of the electric power into heat.

    A heat pump water heater... If the system has access to >~55F ambient air, the typical installation will be at least 2x as efficient vs resistance heating. Of course, they heat a tank of water because it would be impractical to make a tank-less heat pump water heater for a home. In hot climates it can be upwards of 3x as efficient. Plus you get "free" room cooling and humidification (by product of hot water production).

    GeoSpring Hybrid-Electric Heat-Pump Hot Water Heater


    One of our posters (Solar Guppy) has done both solar thermal and heat pump hot water heaters in Florida. His experience has been that heat pump electric water heaters are as cost effective (if not better) as solar thermal and require much less maintenance.

    If you already have A/C for your home, adding a de-super heater to generate hot water is "free" (no added electrical cost) during the A/C season.

    We have one or two posters here that use these for off grid water heating. Program the heater to not use the backup resistance heater--And it takes a few hours to get a tank full of hot water (only ~500 Watt load for compressor/controls when making hot water).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,384 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters
    I am finding a hard time finding how much money one would save when comparing
    traditional electric hot water tank vs tankless vs heat pump tank

    Check out www.energystar.gov

    I am available for custom hardware/firmware development

  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: EVIL electric tankless hot water heaters

    I wonder if I could use rainwater to feed the hot water and avoid the lime build up? anyone do that?
  • pleppikpleppik Solar Expert Posts: 62 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters
    Used to work for a company that among other things, sold tankless hot water to customers who really wanted them. I don't know anyone who was really happy with them.

    Maybe I'm the outlier, but I've had a tankless gas water heater for several years now and I really like it. It has its quirks, but the benefits of unlimited hot water in a house with three teenagers are huge.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: EVIL electric tankless hot water heaters
    pleppik wrote: »
    Maybe I'm the outlier, but I've had a tankless gas water heater for several years now and I really like it. It has its quirks, but the benefits of unlimited hot water in a house with three teenagers are huge.

    We have a tankless propane heater at the cabin. It is ideal for here, especially with just two people.

    They don't like hard water (will scale up easily) or unfiltered water and you do have to make sure they're working properly. Pilot was full of crud on mine this year (it ignites a small pilot with electric spark from turbine before firing main burner).

    The electric ones are just horrible for their huge power consumption.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters
    pleppik wrote: »
    Maybe I'm the outlier, but I've had a tankless gas water heater for several years now and I really like it. It has its quirks, but the benefits of unlimited hot water in a house with three teenagers are huge.

    Ah, but yours is gas fueled and not electric resistance heated. I forgot to say the ones we sold, that no one liked - - were electric. Sorry about that.
  • jebattyjebatty Solar Expert Posts: 56
    Re: EVIL electric tankless hot water heaters

    A regular electric tank water heater can be very efficient and inexpensive to use as compared to how most people normally use their hot water heater. These few things reduced our electric bill for hot water (on a separate meter, easy to see the difference) by 50%:
    1) raise it off the floor and put 4" of foam insulation underneath
    2) wrap it with at least 6" of fiberglass or similar insulation, sides and top, and then cover it with bubble wrap or plastic for appearance
    3) install U-shaped heat traps on both the cold and hot water ports
    4) insulate all hot water pipes that you can get to

    We used about 200 kwh/month before these changes, usage fell to about 100 kwh/month after these changes. The biggest expense of any hot water heater is heat loss through the insulation and piping, plus thermo-siphoning into the cold and hot water lines.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: EVIL electric tankless hot water heaters

    Coming up for our electric tank heater in town: a timer. I figure I can automatically switch it off for half the day (night) and save about $1.50 per day as a result. Two months the timer has paid for itself. After that, gravy.

    While we are at the cabin the tank heater is off. It is the largest single power user in the house now (I ditched the electric stove first thing). It should be interesting to see what the next bill is without having to heat water no one is using.
  • jonrjonr Solar Expert Posts: 1,384 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters

    The most cost effective thing you can do wrt water heating is use lower flow shower heads. With good water pressure, I don't mind < 1 GPM. Such a low rate also means that most tank water heaters provide unlimited hot water (a tankless selling point).

    I am available for custom hardware/firmware development

  • BB.BB. Super Moderators, Administrators Posts: 31,433 admin
    Re: EVIL electric tankless hot water heaters

    Put a teenager in the shower--Low flow shower heads don't save any water or money--Just give longer showers because hot water "lasts longer" and unhappy spouse. :cry:

    -Bill "oh well--this too shall pass" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters
    Coming up for our electric tank heater in town: a timer. I figure I can automatically switch it off for half the day (night) and save about $1.50 per day as a result.

    If it's insulated as described below by Jebatty, don't be surprised if you see very little difference. Some years back when i worked away and only got home on wk-ends, I would shut off my very well insulated 20 gal water heater Sunday morning, leave that night for work, come home again Friday night and there would be plenty hot water for a shower etc. Had a couple inches foam under the tank, and a foot or more of fiberglass around and over it. Also had an inverted trap on the output to prevent hot water from traveling by convection, out into the distribution plumbing. Basically what Jebatty suggested, only more insulation.
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: EVIL electric tankless hot water heaters

    I gotta weight in on this one, since I have worked with a regular gas fired 60 gallon water heater then switched to a solar water heater - with an on demand electric - Tempra 12 heater . . then finally I am running on only the on demand heater . .

    I took out my natural gas furnace, and replaced it with a ground source heat pump, that's when I noticed that the gas bill was STILL - 5 cubic meters a day ! . . just for the water heater. . wrapping it in insulation didn't help. . . turning it down didn't help. . so it had to go. Finally replaced it with a solar water heater / on demand back up . . when I had to take down the solar - running only on the Tempra 12 for hot water . . and actually had my electric bill drop - since the two grundfos pumps would run on and off all day keeping the 60 gallon tank at 170 F . . just too keep the array on the roof from boiling dry. . I am now running completely off the tempra 12 - and I like it for me. . . Now that I have a solar water heater sitting in my garage - I have thought of putting it back up, I know I can get elsid pumps that use very little power - I have one on my radiant floor heat, and it works great - but it is really difficult to find a spot too put it since I have no open real estate to work with . . I had to build a shed just for panels ! Maybe in the future . . .

    I have found out some interesting things though. . if you tried to shower in straight hot water (no cold mixing) - which is what I do with the tempra 12 - you would have to set the temperature of a tank heater really low, and risk having bacteria grow in the warm water - since it's not hot enough to kill the little buggers. . . but since the tempra takes cold water (in my area it drops to around 40-45 F) and ups it too shower temps, no chance of bacteria growing. . . so I just turn it up hot enough for a good hot shower - using no cold water. - and yes, I use a bit over 1 GPM ... good enough for me :p

    So, for my uses, solar water heaters don't make enough hot water in the winter, and they make way too much hot water in the summer - while the on demand electric water heater does use a lot of juice - I am not going off grid - only grid inter-tied for a reason . .

    Funny thing is, I called the Tempra guy too see how much they were, and when I asked him if I could run the tempra 12 on a 100 amp service. . he said "NO".
    Then I explained to him that my heat pump draws a max of 30 amps at start up - if that much - , my mini oven draws 1800 watts, micro wave oven draws 1100 watts, and the washing machine I only run when I am in the room. . . then I asked him again. . . can I run the tempra 12 on a 100 amp service - since it only uses dual 60 amp breakers ?
    He then explained, that in a "regular" house, the hubby and wife come home - the wife starts up the washing machine, pops dinner in the oven, and the hubby hops into the shower. . and under these conditions, no, you cannot use the tempra 12 on a that system. . but, since I know more than most people about the loads I am drawing, yes, I can run a 12 on a 100 amp service.

    Have had it for 6 years now, and would not hesitate to get another one. It's just cool - turn water on - light goes on - turn water off - light goes off. . . no wasted heat (energy).

    Oh, I forgot about laundry (cold water only - see sig at bottom - rain water only) and dishes . . I crank that little thing right up to the max, and turn on the kitchen faucet on slow. . once I get water hot enough too burn me, I crank it over to the cold side, and while it is running full blast - mixing the hot and the cold - there is enough hot water in the pipes between the water heater and the kitchen sink to almost fill the sink at one time. Then I just run it slow to top it up. works for me...

    Just my opinion guys . . :-)
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters

    Hmmmm, 12Kw rated on Homedepot.ca. What do you estimate it uses in a year?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: EVIL electric tankless hot water heaters

    I am not sure about the yearly usage, since I switched to the heat pump / solar / on demand - within about 6 months of each other - only the time it takes to install them . .. (the gas company really peeved me off - so I told em to shove it)...

    What I can tell ya, is the hydro bill for the entire house (all electric) - middle of winter - the highest bill I seen is around 120 $ a month... I can live with that . . . since I try not to do my dishes when ever possible ;) and I take quick showers, probably not a huge amount - I keep the house at 75 F all winter - so the heat pump is alot of that . . compared to that gas unit I had that would come on and heat up. . . cool off. . . come on and heat up . . cool off . . while I am not even home. . . no comparison . . for me anyways. . .

    Just had a thought. . . my last hydro bill was around 45 $ for the month . . whole house.. .lights - cooking - and water heater . . I have a 100 watt blower fan running 24/7 in the basement as well (for the rainy summer) . . almost time for a new house. . any thoughts on where to go for underground house construction ?
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters

    saskabush, lot of old mine shafts from mining Potash...:roll:
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters
    Skippy wrote: »
    Oh, I forgot about laundry (cold water only - see sig at bottom - rain water only) and dishes . . I crank that little thing right up to the max, and turn on the kitchen faucet on slow. . once I get water hot enough too burn me, I crank it over to the cold side, and while it is running full blast - mixing the hot and the cold - there is enough hot water in the pipes between the water heater and the kitchen sink to almost fill the sink at one time. Then I just run it slow to top it up. works for me...

    Just my opinion guys . . :-)
    My tankless (propane fired) has a remotely mounted temperature control. Most of the time I leave it as 120F, and what with the heat losses in the long pipes that is just about right for a shower with a very small amount of cold added.
    When I need to do nasty stuff in the garage sink, I can crank it all the way up to 180F, but I need to warn everyone in the family before I do that.
    The dishwasher has its own selectable heating element to bring the water up to 140F + for sanitation, so I do not need particularly hot water.

    IMHO the biggest problem with trying to combine a solar preheat tank with a tankless heater is that the tankless has to operate at or above a minimum product of temperature rise and flow rate. If that flow rate is not met, the unit shuts down. :(
    SMA SB 3000, old BP panels.
  • mike95490mike95490 Solar Expert Posts: 9,247 ✭✭✭✭✭
    Re: EVIL electric tankless hot water heaters

    I solar preheat to about 140F in summer (heat ex loop in the stove for 90F in the winter) and have a 110F mixer valve at the tankless inlet. My Eternal has a multistage burner, and this works really well, feeding preheated water to it, and just use a bit of propane to boost the temps 10-25 degrees, instead of 50-80 degrees boost with raw domestic water.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: EVIL electric tankless hot water heaters

    Just a question out of curiosity .. What is the usual voltage and current draw of tankless hot water heaters in USA.? Here in Philippines they are about the only type readily available and at low price .. but on full power only draw 8a at 220 v and about 6a half power... More than adequate for hot shower..
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: EVIL electric tankless hot water heaters
    john p wrote: »
    Just a question out of curiosity .. What is the usual voltage and current draw of tankless hot water heaters in USA.? Here in Philippines they are about the only type readily available and at low price .. but on full power only draw 8a at 220 v and about 6a half power... More than adequate for hot shower..

    The ones I used to be involved with had a draw of at least 45 amps @ 240 volts. Colder climate here in Canada results in greater energy consumption to bring up the temperature of initially colder water. In several cases customers had to have their electrical entrances upgraded to handle the extra power. And yes, the lights would noticeably dim whenever it kicked in. They also tended to quickly begin to plug up with mineral deposits - - depending on the water supply.
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: EVIL electric tankless hot water heaters

    While looking for other pictures, I stumbled onto these two . . .

    This one shows the filter - before the unit. . at one point, I was working on the plumbing in the house, turned off the mains, worked on the pipes, turned the water back on . . went too take a shower, and - no hot water. Behind the little set screw, is a really fine screen - and I mean FINE screen . . completely blocked with sediment - from me turning the water back on . . after I cleaned it out, it worked fine - and has ever since. . .

    Attachment not found.

    Attachment not found.

    Here is a pic of the temperatures it can achieve . . . Keeping in mind my unit is the tempera 12 - the smallest . . you can see that by using preheated solar water the GPM goes up significantly . .

    Attachment not found.

    As for the power draw, I have no idea . . it works, and I have never blown out the main fuses in my power panel. . . yet :blush: If anything, a very slight flicker of the lights, but I have too have the heat pump (or the microwave) running at the same time too see it.
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
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