Solar Thermal Hot Water or Tankless Hot Water

72 Posts

Sep 19, 2008 08:44 pm

Looking for advice and help deciding on how to proceed.

We currently use an electric hot water heater, to provide hot water to 4 distinct locations.

1 location uses almost no hot water ( spare bath )

1 location is the clothes washer, and rarely uses hot water

1 location is kitchen sink used daily ... mostly in the late evening + dishwasher ... which is used about twice a month

1 location is master bath for two people with average use of only a couple of showers per day. the showers are almost always in the early a.m. ... long before sunshine. :-)

So, our use is relatively light.

The hot water heater in the crawl space ( which is a different project ... making air tight and solar heating )

Access to the pipes to each location is fairly clear and easy.

So ...

If my largest hot water consumption happens in the early a.m. ... It feels like I'm not going to take advantage of the 'best' hot water that a solar hot water system can provide.

First question ... is this true? Do i understand correctly, that solar hot water systems will not keep their heat ( without other energy source help ) overnight, very well?

And is it true that I should expect to pay around 3k total for the components and installation ( by local,who charges very reasonable hourly rates )

This leads me to think about tankless hot water heaters ... 1 for each of the 4 locations. and getting completely rid of the current electric hot water heater. This way I should save a tremendous amount of energy from standby heating ... and heat loss from transporting through the pipes.

Question 2 ... is this true?

Is it also true that the tankless will end up costing less to purchase and install? Less than 2k?

Mary Sellers-Gray

5 Posts

Sep 19, 2008 09:09 pm

Re: Solar Thermal Hot Water or Tankless Hot Water

Around five years or so ago we switched to a Star electric tankless hot water heater when our propane tank needed to be replaced. We were blessed to get it before the local REA started charging for the larger transformer that needed to be installed at the pole and the larger service wire. My husband is a contractor/lic. elect. & plummer as well as a master cabinet/furniture maker so the rest of the installation he was able to do. It took three 40 watt breakers or 120 watts to run the hot water heater.
The unit began leaking and had to be replaced after one year of use, the next unit did the same. The next unit we also had to replace under the warranty and even tho it was made in Germany it also leaked or corroded at the heating elements. So after three units lasting each around a year a piece we had them switch us to their propane unit. It has been working well for nearly two years though we have noticed it is a gas hog.

This said, all the units have heated the water well. We have almost the same usage as you. Our neighbor installed a smaller gas unit just for their baths in their bathroom and it seems to be the way to go...more units, smaller and closer to where they will be used. If this is the way you go, please let us know how it works out.
Grace and Blessings,
mary

Keith Birchfield

72 Posts

Sep 20, 2008 08:51 am

Re: Solar Thermal Hot Water or Tankless Hot Water

Mary,

Many thanks for your reply and sharing your experience!

Even though I know that gas can be greener than electric ... I'm hoping to completely avoid gas ... I'm very slowly working towards a 'no burn lifestyle' ... trying to 'just say no to gas' ... yes, i know about much of electric coming from coal burning ... working that angle with RE too :-)

Anyways, I'm curious about your comment on 120 watts to run the heater ... did you mean amps? I hope not ... that would be horrendous! Did that heater really burn so much that you had to upgrade your 20 amp service?

Thanks again!

Mary Sellers-Gray

5 Posts

Sep 20, 2008 11:07 am

Re: Solar Thermal Hot Water or Tankless Hot Water

Sorry, you are right, it was amps not watts...I'm thinking light bulbs again. We had to up from a 150 box to a 300 box along with the new larger line to the house to compensate for the hot water heater. I would also like to be gas/propane free here. That's one of the round- tuits...getting my kitchen switched over.

We are thinking of switching to the Marathon high energy saving regular electric hot water heater here on the farm. Our rental house in town we have already done this. Georgia Power has a rebate of $525.oo if you have it installed before Dec.31st. You might pull up your power company online to see what incentives they are offering as well as he feds.

We are also checking out the newer spray foam insulation. A friend had their attic sprayed....the underside of the roof...and in this S.Ga. heat it remained cool in the attic. It is not supposed to be as toxic as the sprays back in the 70's.

Tom M

462 Posts

Sep 20, 2008 12:02 pm

Re: Solar Thermal Hot Water or Tankless Hot Water

Kieth, tanks today are pretty well insulated and can hold their heat overnight. Some tankless heaters are better than others but installation and operation cost, as others have pointed out, can be high. Having endless hot water can be costly too. Since you do not use much hot water, using a tankless may be the way to go. But think of future consequences should units need to be replaced or fixed. Parts or manufacturers may not be available.
Adding solar, to be used in conjunction with your existing electric tank, could work out better. You can go with a smaller system since your requirements are low. Start with a 40-50 gal heat exchanger tank and a couple of solar hot water panels and this should provide all your hot water needs. Use the solar hot water to feed into the electric tank. If the water is hot enough then the electricity should stay off. Then you have all day to make up another tank of solar hot water to be used the next morning and you should end up with 80 gal of available hot water for almost free.

Keith Birchfield

72 Posts

Sep 20, 2008 05:54 pm

Re: Solar Thermal Hot Water or Tankless Hot Water

Mary,
Thanks for the additional tip ... I'll check our provider's site out and see if they offer any incentives.

Also, thanks for the info about insulation ... but I'm thinking about doing something a little different with the attic ... using a radiant barrier to channel the hot air down to the crawl space in the winter ... and out the vents in the summer. Still thinking about this one.

Tom,
Thanks for the encouraging words about tanks being able to 'hold the heat' .... that's wonderful to hear! I would love to use solar thermal instead!

I would especially love to consider a retro-fit, where an exchanger is used.

So, would this hold true for using a heat exchanger to 'heat up' the water in an existing electric tank too? Would a 10 year old tank perform well in keeping the heated water over night?

Tom M

462 Posts

Sep 21, 2008 11:20 am

Re: Solar Thermal Hot Water or Tankless Hot Water

Kieth, I usually do not recommend using solar to heat up the water directly from an electric tank. The two end up competing with each other. If the water is cold before the sun comes out, then the electric heats up the water. Then, if the water is already hot from the electric, the solar will not kick on. Best to keep the solar in it's own tank. If you live in a cold climate, then you would most likely have to use an antifreeze loop for the solar. This would require you to have a closed loop heat exchanger, either external or internal. Some modern heat exchanger tanks are stainless steel and have a lifetime warranty, so they should last. Then you would just have to deal with replacing the cheaper electric tank should it ever fail.

Keith Birchfield

72 Posts

Sep 21, 2008 12:13 pm

Re: Solar Thermal Hot Water or Tankless Hot Water

Would using a heat exchanger on an existing tank still work well?

for example, the one used in this kit:
http://store.altenergystore.com/Solar-Water-Heating/Climate-freezes-Closed-Loop-Systems/Closed-Loop-Systems-for-1-4-People/Closed-Loop-AC-No-Tank/Heliodyne-DHW-System-for-1-2-People/p6756/

Is there a less expensive method?

Ignoring labor for the moment ...

I would love to do something that included 1 panel and a heat exchanger that could be dropped directly on my existing tank. Which is what I think the above is ... sort-of. But my budget may not allow quite that much spent on the parts.

Tom M

462 Posts

Sep 22, 2008 11:10 am

Re: Solar Thermal Hot Water or Tankless Hot Water

Keith, sounds like you are looking for something like the "solar wand". Just do a search. Just be sure your outlet and inlet are at the top of the tank.

Keith Birchfield

72 Posts

Sep 22, 2008 08:53 pm

Re: Solar Thermal Hot Water or Tankless Hot Water

Tom,
Yes. The "solar wand" looks very much like what I was hoping to find ... now I just need to find it for sale. Homepower points to butler sun solutions, so I guess it should be safe from them.

Its a shame that AltE doesn't carry this or other lower cost exchangers. Does AltE carry products by request?

This also makes me wonder how hard a "solar wind" :-) would be to find.

Take the wand principle, but instead of inserting it in to a heater ... fan it out and blow air across it for solar heated air. this way you can use a glycol based close loop system to deliver the energy, and then dump it via air in to whatever space you like ...

Anyways, that's a different project.

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Solar Thermal Hot Water or Tankless Hot Water

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