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Thread: Hybrid v. tankless v. electric

  1. #1
    DIY Junior Member stick man's Avatar
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    Unhappy Hybrid v. tankless v. electric

    Hey everyone.

    I've got a time bomb on my hands. An electric hot water heater that is 30 years old and obviously in need of replacement. My thoughts have gone from installation of an on demand tankless (would have to be propane, as I am very rural), to hybrid heat pump tank style, to simply replacing my electric tank with another electric tank heater.

    What has caused the waffling has been the lack of proof that an on demand tankless propane system would be any more efficient than a hybrid. The cause for pause on the hybrid model is the lack of track record that the hybrid will not give me headaches 2-3 years down the road. And that leaves me with the old stand by electric tank replacement.

    Any thoughts on a tankless lp system?

    How about durability of hybrid systems?

    Electric Tank Mfr/Models that are supperior?

    I've a family of 5 (3 tweenage daughters = many showers on the horizon) with 2 baths.

    Let's hear it.

    Thanks
    stickman

  2. #2
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    With 3 daughters that age I would go with LP tankless...maybe 2 of um. And a big lp tank.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    In Idaho, your wintertime cold water temps are likely near freezing. To get a decent rise, you may need two of the things in series especially if there would be more than one shower at the same time going on. They also require periodic maintenance to remove built-up minerals like cleaning up your teakettle or coffee pot after awhile. A hybrid is essentially a heat pump. May not need maintenance often, but it's mechanical with moving parts, so yes, it will need maintenance periodically as well. Depending on your electric rates, the hybrid gives you more heat per Kw than a straight electric, but a straight electric is basically no maintenance for a very long time. When you add the cost of installation of tankless, along with a propane tank, if you don't already have one, it may never pay off in the end. A hybrid might pay off before it dies. By far, the simplest is to just replace the electric tank with a new one. Depends on what your power costs are.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Master Plumber master plumber mark's Avatar
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    why not make it easy on yourself and just install another 50 gallon electric water heater
    itwill probably be good for another 30 yearsa... what more could you ask??/

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    A man living with 4 women......3 daughter and I assume a wife. You better go with somthing that can provide alot of Hot H2O.

    IF you know whats good for you. LOL

  6. #6
    In the trades Dana's Avatar
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    Quote Originally Posted by stick man View Post
    Hey everyone.

    I've got a time bomb on my hands. An electric hot water heater that is 30 years old and obviously in need of replacement. My thoughts have gone from installation of an on demand tankless (would have to be propane, as I am very rural), to hybrid heat pump tank style, to simply replacing my electric tank with another electric tank heater.

    What has caused the waffling has been the lack of proof that an on demand tankless propane system would be any more efficient than a hybrid. The cause for pause on the hybrid model is the lack of track record that the hybrid will not give me headaches 2-3 years down the road. And that leaves me with the old stand by electric tank replacement.

    Any thoughts on a tankless lp system?

    How about durability of hybrid systems?

    Electric Tank Mfr/Models that are supperior?

    I've a family of 5 (3 tweenage daughters = many showers on the horizon) with 2 baths.

    Let's hear it.

    Thanks
    stickman

    Efficiency is one thing, cost of operation is another. At current pacific northwest prices propane burned in a 0.90EF tankless is roughly equivalent in operating cost to heating water in a 0.90EF electric tank with 12 cent/kwh electricity. If you're power is cheaper than that, odds are you'd be spending more money to heat water with propane.

    The hybrid electric tanks with the tanktop heat pumps are not a great option in heating dominated climates, since they draw half the heat for the hot water from the room-air, representing a very real load on the heating system. That's fine if you're heating with a relatively cheap fuel, not so much otherwise. They also revert to resistance-electricity for more rapid recovery, so in high hot-water use situtations they're not much more efficient than any other electric tank heater.

    With the prospect many showers on the horizon, there is real cash payback in drainwater heat recovery heat exchangers, given your HW heating fuel options, and extends the showering time available from any tank heater considerably. They raise the temperature of the incoming cold water about half-way to showerhead temp, and when plumbed so that the output goes to both the cold side of the shower AND the cold side of the hot water heater you get maximum function & efficiency out of them. It would turn any propane-fired tank with a 40KBTU/hr burner into an endless shower situation just like a tankless, and it would cut the recovery time for an electric time roughly in half, while extending the initial showering time by a significant fraction.



    Natural Resources Canada maintains a third-party tested apples-to-apples efficiency comparison between different vendors & models at 2.5gpm shower flows.

    Most of the vendors are in Canada, but will ship to US addresses. EFI is the US distributor for PowerPipe, and ships from their facility in WI. (They will open an account for you with a cc # and will ship them quantity 1.) There are efficiency rebates available to those who currently heat hot water with electric tanks, but SFAIK not in ID (but next door in OR, yes.).

    Whichever way you go on this, the payback is going to be there for you, if not for a 2 person family heating water with cheap natural gas. The taller and fatter the better- the enhanced efficiency of the bigger units makes them pay back sooner than with smaller, lower efficiency units, despite the increased upfront cost. A 50% efficiency unit turns an 0.90EF water heater into a 1.4EF unit, at least for showering draws (which will probably be at least half your hot water use when you have teens in the house.)
    Last edited by Dana; 03-23-2012 at 10:53 AM.

  7. #7
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by master plumber mark View Post
    why not make it easy on yourself and just install another 50 gallon electric water heater
    itwill probably be good for another 30 yearsa... what more could you ask??/
    Absolutely true and your hands down life cost effective solution. The tankless are bad jokes. The hybrids are unproven but proven to be over mechanized which means big repairs.

    What Dana said, ELECTRIC, and with or with out the drain job heat grabber.

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    50 gal electric is not large enough for 5 grown people.

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    In the trades Dana's Avatar
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    What Hackney said- 75 <--> 100 gallons if electric, (and definitely drainwater heat recovery if you have at least 36" of vertical drain to work with.)

    The 85 gallon Marathon (~$1K at box stores) delivers 90 first-hour gallons, and with drainwater heat recovery would deliver about an hour's worth of back-to-back showering duty compared to only ~40 minute's worth without DWHR. Even if run into the tepid-zone with endless showers, with DWHR the recovery time would be similar to a 50 gallon unit that had the same 4.5kw elements run to depletion without benefit of DWHR (or maybe even a bit quicker.) With 85 gallons somebody could even run a bath and there would still be some showering capacity left, but not so much with a 50.

    But if it's a slab-on-grade house with no possibility of DWHR you'd be looking for at least 100 gallons to keep the girls from killing one another.

    Tip: Put the bathroom lights on an occupancy sensor switch, and adjust the time-out delay to 8-10 minutes as a cue that maybe the shower is running a bit long. (It hasn't cured my kid of the endless shower habit, but it saves quite a bit on the "But I just started." line of argument. :-) )

  10. #10

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    3 girls plus wife and me and and 80gal electric tank on off peak electric and have never run out of hot water. Electric off peek rates around here running about 5 cents so propane cant even touch that rate. Can you get off peak where you are?
    Politicians are like diapers. You need to change them often……for the same reason.

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    I lived single for about 6 years and would burn through 50 gallons with a cold water temp of 70 degrees and a outlet temp of 135 on a regular basis. When I was home I was washing clothes,showering,brushing teeth,filling jetted tub and maybe washing dishes. I live alittle bit different now. LOL

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by Hackney plumbing View Post
    I lived single for about 6 years and would burn through 50 gallons with a cold water temp of 70 degrees and a outlet temp of 135 on a regular basis. When I was home I was washing clothes,showering,brushing teeth,filling jetted tub and maybe washing dishes. I live alittle bit different now. LOL
    If you've lived your entire life where the incoming water temp is 70-degrees, you don't know the problems of places where it is closer to freezing. Some people with deep wells experience that nearly all year, while lots more get it during the heart of winter and into early spring. It requires a different mindset and design criteria if you want or need lots of water.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Quote Originally Posted by jadnashua View Post
    If you've lived your entire life where the incoming water temp is 70-degrees, you don't know the problems of places where it is closer to freezing. Some people with deep wells experience that nearly all year, while lots more get it during the heart of winter and into early spring. It requires a different mindset and design criteria if you want or need lots of water.
    I dont have to live where the incoming water temps are cold to understand the problems. I'm a trained professional Master Plumber.

  14. #14
    General Engineering Contractor ballvalve's Avatar
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    But if it's a slab-on-grade house with no possibility of DWHR you'd be looking for at least 100 gallons to keep the girls from killing one another.
    I want to know who taught these girls they stink so bad after a hard day driving their cars and chatting at the McDonalds? this abberant world we live in is the first time in history ANY human has had to shower -and most absurdly- wash their hair every day with 20$ shampoo. Dish soap works the same. And a wet rag will do all the netherworld with 8 ounces of water.

    NOT what hackney or Dana said. One 40 gallon rig at 160 degrees and both elements running together with a tempering valve will allow this family to help destroy the natural enviromant. And [3] yes THREE 40 gallon cheapies in line are far less cost than one 100 gallon heater.

    I'd give these sweet smelling girls a 40 gallon unit at 130 degrees, and let them stagger bathing or learn how to do it the historical way.

    I am a trained professional muckraker. I don't give a whit about incoming water temperatures. I care about people conserving what's left of our enviroment and stopping population growth before the towns in Kansas look like Hong Kong.
    Last edited by ballvalve; 03-25-2012 at 03:07 AM.

  15. #15
    In the trades Dana's Avatar
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    This is a 2 bathroom house- two showers running at a time will drain a 40 gallon electric pretty fast even at 160F storage temp unless there's some drainwater heat recovery (and even then it's an issue.) The standby loss at 160F is nearly 2x that of a 120F tank too.

    The standby losses of a 85-100gallon tank @ 120F isn't appreciably more than a 40 gallon tank @ 120F, and operational cost of heating the water will be the same. What you get out of the bigger tank is guaranteed peak capacity to ensure the civil peace is maintained. (Priced family-counseling or divorce lawyers lately? :-) )

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