Should I get a tankless water heater?

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  • colderthan
    colderthan Registered Users Posts: 20 ✭
    #32
    Re: Should I get a tankless water heater?

    We also considered replacing our 40 gal propane w/h with a tankless. like you a very low water use household.

    Our solution was to add a 10 gal electric close to the point of use and install a shut off valve on the other w/h. This is plenty for a shower or dishes.

    Replaced the 110v 1800w heating element with a 220v that uses about 650w @ 110v. perfect dump load for our 1000w solar . Takes about 2 hours for it to heat to 160 deg.

    Still have the option of using the big w/h if needed, but this very seldom happens.

    This has worked out very well for us, much cheaper than a tankless. Your milage may vary.


    Paul
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #33
    Re: Should I get a tankless water heater?
    rogerlollar wrote: »
    I have two tankless propane water heaters serving different parts of the house. They are three years old and work very well. I am considering putting a self built "batch" style solar water heating in front of and therefore feeding a tankless water heater in the new home I plan to build soon. This should significantly reduce the amount of propane necessary to heat the water to 120 degrees. Anyone have experience with such a set up? Any Comments?

    I just do not see the effort to do this being any more than a "kind of good thing" to do. If you really want to heat water you need a tank and enough collectors to heat the water the way you want it. Your on demand is the back-up. I think alot of people get caught up with on demand heating saving them money and miss the big picture. If you want to save energy here, you have to use the sun and you have to have a tank that will hold the 120F heat until the next day. Anything else is just back-up!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #34
    Re: Should I get a tankless water heater?

    Dave,

    I respectfully disagree. While there is a diminishing returns aspect if you only use tiny amounts of water, the fact is that every BTU put into the water by the sun is a BTU you don't have to use other fuel for.

    Rogerlollar's suggestion of a batch type preheat system has, IMHO, great merit. (Depending on the climate). A simple ~50 gallon steel tank, in an insulated glazed box, in a location with lots of sun can pick up a huge number of BTUs, with no outside energy required to move it. Simple (and cheap) to build, and simple to operate. In freezing climates, (if there is a risk that the tank would freeze, but with the mass, it would take a long time,, not overnight except where I live! just drain it and bypass it.

    So a demand water heater is ideal for using preheated water. For example, if your city or well water comes into the house ~55 f, and you want water at 120, you have a 65f rise. If your preheat tank can deliver water to the demand at say 85, you have just reduced the amount of propane (or electric or natural gas) required by nearly 1/2. Not bad for what will be pretty cheap to build.

    Tony
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #35
    Re: Should I get a tankless water heater?

    Hello Tony,

    I do not think you need to disagree because we do agree. I said that I do not see the effort as being any more than kind of a good thing. That is not to say that it is not a good thing!

    I have no idea of where the climate/latitude of the OP lives but if it is average and he is asking my opinion, it is a no brainer to heat water with solar, store it in a controlled environment, and back it up with a gas source.

    A batch heater with the tank outside in my mind is for the southwest and limited in other areas to be a pre-heater. Solar hot water is just too easy to design as a full time heat source for most of the year. That is why the tax credits are there. It is easy to provide full time hot water with a couple of 15 watt pumps for 2/3's of the year or more! It does cost more as you go north but it is easy!

    Kind of a good thing, and a very good thing. Budget and perspective are the drivers. I want that tank inside full of really hot water. That is how I advise my clients and friends!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #36
    Re: Should I get a tankless water heater?

    Heat loss from modern storage style well insulated water heaters is very low - there are losses between the tank and the point of use that can be significant.

    My solar thermal system electric backup used - 163 kWh in January, 93 in February, 51 in March and on 18 March İ pulled the plug to the auxilliary heating element. The electric backup maintains a 50 deg temperature (120F). İ will plug it back in sometime in November. Good deal as far as İ am concerned!

    The only gas available in my location is LPG and that is priced as road fuel - more or less 12 USD per gallon gasoline equivalent - not very practical!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #37
    Re: Should I get a tankless water heater?

    Dave's just saying that if you make the effort to put in a solar water heating panel you might as well add the storage tank and maximize its potential. I agree; it's not that much more to add and as Russ points out the retention efficiency available today is very good.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #38
    Re: Should I get a tankless water heater?
    russ wrote: »
    Heat loss from modern storage style well insulated water heaters is very low - there are losses between the tank and the point of use that can be significant.

    My solar thermal system electric backup used - 163 kWh in January, 93 in February, 51 in March and on 18 March İ pulled the plug to the auxilliary heating element. The electric backup maintains a 50 deg temperature (120F). İ will plug it back in sometime in November. Good deal as far as İ am concerned!

    The only gas available in my location is LPG and that is priced as road fuel - more or less 12 USD per gallon gasoline equivalent - not very practical!

    Good point Russ! The electric back-up can work and make sense if the solar is heating the water by itself most of the year. For offgrid you could never do that though. Tony might tell you that your monthly KWH in Jan would have run his home for six months. If you have the grid there are other options I am sure! My advice is often (ok always) slanted for offgrid. I can barely remember what having grid power was like.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #39
    Re: Should I get a tankless water heater?
    Dave Sparks wrote: »
    I can barely remember what having grid power was like.

    1. There's a great big BILL every month, and I don't mean our illustrious moderator comes 'round for coffee.
    2. There's a rate hike every year.
    3. When the power goes down, you have to wait forever for someone else to fix it.
    4. Brown-outs damage your most expensive equipment.
    5. There's a great big BILL every month, and I don't mean our illustrious moderator comes 'round for coffee.

    :p
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #40
    Re: Should I get a tankless water heater?

    I am a cheap date...

    -Bill "moderator" B. :roll:;):D
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #41
    Re: Should I get a tankless water heater?
    BB. wrote: »
    I am a cheap date...

    -Bill "moderator" B. :roll:;):D

    Wait until the economy picks up and then threaten to quit! When is that suppose to happen?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #42
    Re: Should I get a tankless water heater?
    Cariboocoot wrote: »
    1. There's a great big BILL every month, and I don't mean our illustrious moderator comes 'round for coffee.
    2. There's a rate hike every year.
    3. When the power goes down, you have to wait forever for someone else to fix it.
    4. Brown-outs damage your most expensive equipment.
    5. There's a great big BILL every month, and I don't mean our illustrious moderator comes 'round for coffee.

    :p

    Thanks Marc! I heard a jet go by 3 days ago. Add that to the list!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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