There is no doubt that of all the options available for capturing and using solar energy, passive solar hot water heaters give the best bang for the buck.

In Hawaii interestingly enough they are now mandatory.

Hawaii to Require Solar Water Heat in New Homes
Posted: 2010-01-04
Effective January 1, all new homes built in Hawaii will require the installation of a solar water heater to meet the state’s green building mandate, which was enacted in 2008 and slated to become effective in 2010.

Signed into law by the state’s Governor, Linda Lingle, the law actually requires energy-efficient hot water systems, but most builders and environmentalists agree this implies solar hot water, since no other residential type – including tankless water heating and heat pump water heaters – provides quite so much conservation bang for the buck, with greater reliability, as solar hot water.

The ruling is expected to save homes an average of 30 percent energy yearly over conventional homes with gas or electric hot water heating. This is good for homeowners, 30 percent of whose energy bill is devoted to heating water, and for Hawaii, whose almost total reliance on imported oil (99 percent in 2006, and little improved since) creates a precarious energy security scenario that has politicians nibbling their fingernails.

Here's a quick graphic I created that shows how a passive system works.

I'll get the ball rolling here...

Growing up on the farm in Australia in the late 70's, we had a wood fired boiler for hot water and space heating. We then put some solar hot water panels on the roof , three 5'x5' flat panels, and saw a significant decrease in our wood consumption. The area, near Canberra, the capital, has cool but sunny winters. The mid winter wood use went down a bit, the spring and fall wood use was probably halved, and in summer (lots of sun and no space heating) we never had to fire up the boiler, and actually had enough excess to divert some to the swimming pool.
We did get winter frosts, and the boiler and hydronic heating system already used a glycol/water mix, so this was easy to connect to the panels.
The panels operated without a hitch for the next ten years we were at that house, and saved me countless hours of woodchopping. And this was the 70's, todays panels deliver much better performance

Many houses in Australia had solar systems back then (and more do today) . When I first mentioned them here in Canada, people looked at like I was from another planet, but they are slowly gaining acceptance. For any cold climate, I would not use anything other than the evacuated tubes, they maintain performance in sunny days even at -20C.

The City of Vancouver has recently passed a building bylaw requiring all new houses to have ceiling rough ins for solar water heating.

The best advice I have heard, is to not oversize your system. You can never design it to completely replace conventional hot water, though it may do this in the summer. A well sized system will provide the bulk of your hot water in spring/fall.

If you are sizing for winter space heating, then make sure you have some way to "dump" the excess heat in summer, or cover the panels. I have heard of systems boiling in the summer!

As always, the cost/payback depends o what you are replacing. if it is natural gas, it's a long payback, if electricity, propane or oil, then it's quite good. Wood, well, it depends how much exercise you want to get, or want your kids to get...

I suspect these systems can be installed for a lot less by a handy do-it-yourselfer.

In calculating capital cost, don't forget to deduct the cost of running a gas line if the only gas you are using is for water heating. This can save $1000 or more.

In calculating savings, if you are only heating water your payback will be good because you will be avoiding monthly connection charges for summer when you will be paying several times more fore service than for the actual gas.

The roof is a bad place to install these systems. You risk leaks and there are higher wind speeds. A ground mounted system can be better protected and you can repair it yourself. Most accidental household deaths are caused by falls.

We have had solar hot water panels for 28 years, and recently replaced the panels as there was some deterioration and one panel of four was lost to frost damage a couple of years ago. The original panels were reasonably effective, and clearly reduced electricity usage (off peak heating). Maintenance over the years has been occasional replacement of circulation pump or impeller, one repair of the controller due to a failed capacitor, and one replacement of heat sensors.

However, the heat input from the replacement panels is far greater, so much so that I should be putting shade cloth over one of them in summer. The tank can peak around 90C - You can just about make tea from the hot tap (and you definitely could if you were in the US!) The boost power is turned off unless we have 2 or more days of complete overcast (unusual here in Sydney). If I turn off the circulation pump, the panel temperature goes beyond 140C - I didn't like to continue the experiment above that temperature. The area of the new panels is slightly greater than the old, but the glass is better (low iron) and the panels seem to radiate less. They are flat panel construction, not evacuated tubes. The area is around 2msq.

The replacement panels with all sensors and controller cost around $AU1200, so not expensive.

My experience of solar hot water for 28 years is that it is very cost effective, and current panels are amazingly good, at least when new.

When looking around for replacement panels it seemed that evacuated tubes were favoured against flat panels. My experience is that flat panels are very effective, more than good enough, and much cheaper.

A modification I am considering is adding a second glazing layer with perhaps a slightly narrower transmission window than the glass provided. On clear winter nights the panel temperature drops well below ambient, requiring water circulation to avoid freezing even on quite warm (10-14C) nights. The temperature drop is due to radiation into the cold night sky (we can have humidity of 20-30% at night here in winter). A second glazing layer would also reduce summer heat input a little, which would be a good thing.

If I move from here to a place without solar hot water, it'll be one of the first items I'll be adding.

Once again, Homepower is hard to beat as a reference on all things renewable. Here's an article for general understanding and selection of SHW systems:

http://www.homepower.com/view/?file=HP125_pg92_Marken

Our system (currently undergoing an upgrade) is a simple "drainback" active system. The solar heated water is stored in a tank. Our domestic hot water is pre-heated through a heat exchanger in the tank and then goes through a tankless water heater. Most of the time the tankless heater doesn't turn on as the water is already at or above the 122 degree setpoint after going through the storage tank. The "drainback" system means that no water remains in the collector when the system isn't warm enough to produce hot water. The water just drains back to the tank. This eliminates the need for a glycol solution. The system also supplies our radiant floor heating.

Other great articles from Homepower:

Regarding storage and tanks:

http://www.homepower.com/article/?file=HP131_pg70_Mehalic *

About types of collectors:

http://www.homepower.com/article/?file=HP133_pg30_ATE_3

http://www.homepower.com/article/?file=HP133_pg70_Marken *

http://www.homepower.com/article/?file=HP132_pg40_Mehalic *

Pumps and plumbing:

http://www.homepower.com/article/?file=HP134_pg98_Mehalic *

(asteric denotes subscription required, IMO worth it)

i snagged 4 copper panels[w/ tubes built in- but no glass or box frames] which came from 70's solar hot water heaters.

i think they are about 2 1/2' X 8'. we live where optimally we'd do the glycol[ mix], but i want to keep the system as simple as possible, & dollars are tight.

hadn't planned on moving forward yet so i haven't done much thinking/research. any particular suggestions, or links will be welcomed. i'll certainly look forward to the info this thread will have. thanks.

When our LPG water heater broke 3 years ago we replaced it with a solar water heater and no backup. The SWH is a passive thermosyphon model with 21 evacuated tubes and a 150 liter storage tank plus 30 liters in the solar tubes. This is for a house with 3 persons living in it. It has worked extremely well, with no backup the hot water temperature has only gone below 40 C on average 5-7 days per year, and even then it is still possible to take a shower without much suffering, but you have to take into consideration that it is installed in the south of Mexico where the ambient temperature rarely goes below 15 C.

It was very difficult to find a knowledgeable contractor, I ended up installing it myself, the installation instructions where very confusing, the hot and cold water lines were mixed up in the diagrams, and the vendor was not very helpful, he even discouraged me from getting one, it was only because I was determined to get one and knew what I wanted that I was able to buy one.

The cost of the SWH was about $600 USD plus installation, which I can't remember exactly but it was about an additional $100 USD. I figure that I am saving about $100 USD per year on LPG so it will pay for itself in 7 years or less because the LPG price keeps going up.

In conclusion I am very happy with my SWH. It requires less maintenance than a gas heater, its cheaper to operate and I figure the investment was better than putting the money in the bank.

I'm amazed that there is no mention of solar pre-heating. It seems to me that solar hot water is being presented as an either/or option. In our case, we've had solar pre-heating for at least 25 years and have a heat exchanger in our wood heater that pre-heats the water in the winter. And, I might add that everything was designed and installed by me. There is a very detailed TOD archive on how I built my collectors some place. They follow the roof line and don't stick up.

Yes, I do have an intermediate tank (and in my case a pump - which draws all of 42 watts). Although I do have a differential temperature controller system, I've simply switched to turning the pump on when it is appropriate- either manually or via a timer.

Todd

As a PS, I do use my PV to heat the regular (220volt) water heater using a timer. I think it is in my key post A Trip to Todd's as to how it works. If you can't find it, and are interested, I'll post more.

Our house, which we bought in 2004, has a 'Copper Cricket' solar water pre-heater which is not made anymore. This system utilizes the 'geyser' principle in that the pressure from the heat itself drives the solar loop, with the collector above the water tanks. In other words, no moving parts, no electricity, no pumps, etc.

It's really too bad that the inventor (as I understand) ran into problems in the patent world and stopped making these systems. In our community there are 6 of these systems, some having worked without problems for ~20 years. All they generally need for maintenance is a flushing of the water loop every season, and, of course, a replacement tank if the tank shows signs of rusting through.

Mid summer brings electric bills $10-$20 lower than the bills in winter.

Hi Gail, SHW does indeed have the potential to provide cost effective renewable energy. It is a pity that in US so many of the heaters are used for swimming pool heating; in China, which has over half of global installed capacity of SHW, the majority heat domestic hot water systems (IEA, 2009).

For a summary of SHW from the UK's perspective, please download and share an academic article I wrote but did not publish on the subject, for which I received 72% at the University of Sheffield's E-Future's course. I believe this report, and the IEA's authoritative (2009) analysis of SHW presented here provide interesting and relevant background information on the true significance of SHW from an international perspective.

Keep the Drum Rolling, Robin

When we had nothing better to do (all crops were in), we dragged a defunct hot water heater from the scrap heap, peeled half the jacket and insulation back, painted that half of the naked tank black, rolled it onto a pallet against the south side of the pumphouse, with the bleed valve on top, ran a water line from a tee in the pumphouse through the wall to the tank inlet valve, and an underground water line from the outlet valve to the house, then built an insulated cold frame around the tank, with an aluminum frame window, also from the scrap heap.

In the house, we simply connected the new line to the hot water heater supply line via a tee and a gate valve that can be shut off if anything happens to the outside system.

The safety drain valve becomes the bleed valve in this arrangement; otherwise you may trap air in the tank, reducing heat efficiency and possible causing pipe hammer. To drain, disassemble cold frame, unhook the feed lines, and roll the tank over till the valve is on the bottom; open the valve. Needless to say, the valve inside the house should be shut off before working on the exterior system.

Perfect? No. But not an exercise in futility; this setup gets hot about half the year, and its use is as a pre-heater for the hot water heater. The electric bill has diminished as anticipated; we think we make back our original investment of about $40, three to four times/year.

Solar domestic water is good for Hawaii, Florida and southern California but not cost effective elsewhere.
Any place with any amount of cold weather needs high efficiency evacuated tube type with a pump and of course a back up water heater. An average apartment might use 40 gallons of hotwater per day which can be handled by a 40000 Btu (backup) gas hot water heater(50% efficient). Annually that's ~24000 cfh of gas per year or $200 per year.

In the northern half of the contiguous USA in Dec, Jan , Feb you can produce about
3500 Btu/month/sf, the rest of the year closer to 7000 Btu/ month/sf. In the summer, 150 sf of evacuated tube would produce 35000 Btu per day. A 150 sf evacuated tube system would cost ~$10000 and it might handle about 2/3 of the annual domestic water heating or $133 per year.
The payback isn't very good at current energy prices.

JMHO

I have a brother with a 5 panel (4x8) solar thermal system. It heats his water and also has an exchanger that sits inline on his gas fired air furnace (retrofit). So he can run the blower only for the first few hours after a sunny day to heat the house with the btu's stored in his tank. WIth the proper orientation (south) and a good amount of windows, his furnace hardly runs on sunny winter days. He put this up when the first subsidies in Illinois were available around 2003-04. He has something like an 80 or 120 gallon tank (drain back style) which stores the hot water and their is another heat exchanger to heat his traditional gas fired hot water heater. From mid April through most of October the only gas he uses is for cooking. The first year, the gas company came out and to check to see if he diverted around the meter as his gas usage was down so dramatically as winter progressed.

The key is having the appropriate solar window to the sun and siting it properly, though with solar thermal this is a lot less sensitive that using solar pv. In many cases instead of using the solar PV rule of thumb of having the tilt at you latitude for fixed mounts, you generally want to plus that by 5-10 degrees to maximize for solar gain during winter. In summer, you will produce more btu's than you can use. As always specific site analysis always trumps rules of thumb, so if you have real cloudy summers and clear winters this may not apply.

It was a big missed opportunity after the 70's energy crunch when solar thermal was all the rage for a few years that more municipalities did not set up guidelines to require most subdivisions to have most of the homes orientated so homes were built with a south orientation for the long axis of the hours. Take a look at how older homes (100 + years were orientated). But then again, I am discussing suburbia...

There are a number of trade offs comparing evacuated tubes and flat plate collectors. Evacuated tubes are somewhat modular, so if a kids ball hits the panel you may break one or two tubes but the unit itself will continue to produce hot water. They are also capable of producing higher temps, though for most residential this is not a concern and if you don't have the proper storage, a waste. Also in high snow areas with inaccessible panels (roof), the snow will melt off the evacuated tubes faster than a flat panel. Flat panels will not produce as much heat (per sq. ft of area) as evacuated, but are less expensive.

Here is a link to the feds site http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850

And the wiki http://en.wikipedia.org/wiki/Solar_water_heating

A couple of links of people who've designed their own homes with solar thermal (and PV).

http://www.daycreek.com/ - He provides a journal of his house building and PV - Thermal design process and installs. (Caution, you may spend the next week reading his journal).

http://www.ourcoolhouse.com/ Another journal of home building process and design. Allows builds and sells solar thermal monitoring solutions and parts you can use to make your own system.

I went looking for a solar hot water system in the summer of 2008 (I had just filled my fuel oil tank at $4.25/gallon). The local solar store had free two hour seminars each weekend, so I signed up for one. I also began doing on-line research - there is certainly no shortage of info on the web about solar hot water heating.

The guys at the solar store were great - good info - not pushy - just salt of the earth types. They came out for an estimate with some cool tools for calculating insolation, etc. Some trees would have to go...but the south facing roof was a winner. I looked at their proposal - good quality flat panel equipment installed by a well known local plumbing/heating/HVAC contractor. I signed up...and then it took 3 months to get the work scheduled due to the high demand.

They were in and out in a day, 3 roof mounted flat panels, glycol closed loop, AC controller, a new 110 gallon tank, wired and plumbed into my existing boiler (for backup). Neat, polite, personable people. All Stiebel-Eltron equipment. They took care of the town plumbing permit - also, I believe in Massachusetts, there is no sales tax on solar equipment, and (supposedly) a property tax exclusion for solar equipment added to your home. These were not factored into my decision, but nice added benefits.

Small problems...the trees to be removed were actually on my neighbor's property. They were supportive about the whole idea (I gave them most of the resulting firewood). But the tree contractor added almost $1000 to the cost....though I got some side benefit, landscape-wise. The guys put in the wrong glycol concentration and came back a few days later to drain and refill...no big deal...but I'm glad they caught it...it can get well below 0F in western Massachusetts in the winter.

Just under $10,000 for the system. Minus $3,000 in state and federal tax credits. I figured the payback for a family of five at 5-7 years, a little longer now as the price of fuel oil has dropped. I self-financed, though the solar store guys did have a pretty good low interest loan deal with a community bank to spread the cost over 5 years. It gives me great pleasure to never hear the boiler run most of the summer. Like some of the other posters, I regularly see the panels at 180+F in the summer, and get home from work to find 110 gallons of 165F water in the tank (this will go about 2 days with my family - if it's sunny at least every other day in the summer, I'm not using any oil at all). In the winter...well it's New England...but on a sunny day in December the panels will reach 120F...still pretty good. I'd estimate I get 90% of my hot water "free" in the summer, and maybe 40-50% in the winter. Some behavior modification could maximize use of the solar gain (like showering in the afternoon, etc), but with 3 teenagers...I am just happy with the gains I get without rocking the boat.

Still very happy with the decision - zero problems so far - I took my time, and made sure I got quality equipment and contracting. I expect those panels to still be making hot water in 25 years. I also burn wood for heat, drive a small car, use CF bulbs...not necessarily for the green factor...but as financial decisions. The engineer in me finds it a challenge to try to reduce my family's oil/energy consumption. If you have a south facing roof (or room on the ground for the panels), a solar hot water system is a very practical, low maintenance way to harness the power of the sun.

I'm in Ohio and have had solar hot water for over ten years. I bought a used set of panels, contacted a local person who had been active in the 1980s, and got a system up and running for a total of about $3k. I've had to replace circulator impellers and one external heat exchanger - but had been warned that our water is so hard that without a water softener this was bound to happen. I estimate that it covers 1/2 to 2/3 of hot water needs for my family of four. The system has an on-demand water heater as backup; that unit modulates to only heat the incoming water to a set output temperature.

Since installing that system, I've helped install another 5 or 6 systems locally, always with people who wanted to learn themselves and were mechanically handy. I'm not licensed, and wish more people around here were. We pieced together used collectors and sometimes tanks, usually bought commercial controllers (Steca makes nice, fairly inexpensive units), and have tried glycol systems, drainback systems (careful about freezing and getting good draining; ask me what happens if you don't), and systems integrated with radiant floor heating. Everyone is happen with what they have.

For me personally, I still get a little thrill on a sunny day when I see that the pump is running and that I am getting "free" hot water. That's worth something as well. Although it's not going to work for everyone, as an acquaintance in Germany told me twenty years ago when I first learned about solar hot water systems, "nobody asks about the payback time for the sunroof on the car or for the granite countertop in the kitchen; you do it because you want to." I'm afraid we still often hold renewable energy technology to a higher economic standard than many other things we undertake daily.

We live in southern Ontario and have two active panels ground mounted off the back of our home. The installation is described in greater detail in the posts on my blog at http://www.juniperrock.ca/wp/?cat=6

In the winter, I estimate that solar provides 25% of our domestic hot water (with the balance electric) while in the summer it can supply close to 100%. The issue is not outside temperature (the insolation does not differ that much). The percentage of sunny days does differ a lot summer to winter.

Our system cost approximately $5,000 Canadian installed by a professional installer.

We put in an Indirect circulation system over a year ago in Auckland NZ.

We chose the indirect system but we use water as the heat transfer fluid for 2 reasons.

1. Not being glycol, if the closed circuit happens to leak you only get water leaking into water. A plumber mate told me horror stories of a family that had used glycol, had a leak and the whole family came down with a range of neurological symptoms.
2. By using one charge of water in the closed loop we get only one dump of dissolved chemicals into the loop. If you use direct circulation each new flow of water brings new chemicals that get deposited to shorten the life of the system or require more frequent cleaning.

The system we have also has a reverse flow setting for places where there are light frosts. It moves water from the tank through the loop to keep it from freezing.

We get value from it all year round but we essentially turn off the electricity to the tank from about mid November till the end of February.

It uses mains pressure for the tank and the backup coil is half way up the tank so that it heats the least amount of water possible to keep the temperature up when the solar is short.

Only thing missing is PV backup for the pump which needs about 25 watts; that's next on the list.

We have a solar water heating system, in Austin. I bought it as a kit from http://kingsolar.com (their web site seems to have imploded to just a phone number, but my experience with them was good). Total cost was about $3,000 since I installed it myself; this is a good do-it-yourself project for those who are moderately handy. The cost is about twice that if a contractor installs it.

The system has a 4x10-foot panel, an electric water heater with a heat exchange loop inside it also, pump and controller. The controller compares the temperature in the panel with the temperature in the tank; when the panel is 10 degrees hotter, it turns on the pump. The hot water from the panel flows through the heat exchanger loop and heats the water in the tank. Basically the pump runs all day when the sun is shining. The panel loop contains about 3.5 gallons of water and Noburst non-toxic antifreeze [car antifreeze is toxic and should not be used], although fluid in this loop is contained and normally should never mix with house water.

From about April until sometime in October, I turn off the electricity at the breaker, and solar provides all of our hot water. In the winter, sometimes electric backup is needed, but the solar helps a lot. In summer, the system can even get too hot and boil over. There is a "tempering valve" to add some cold and prevent scalding; the tank temperature sometimes gets up to about 160 F.

Our house is all-electric. Electric water heating used to use about 13 KWH per day, or about $40 per month, so the payback is 4+ years, with 30% Federal tax credit. Definitely cost-effective. The pump and controller only use about 0.3 KWH per day, or $1 per month.

Compared to photovoltaic solar, which we also have, the solar thermal saves as much electricity as a 3 KW solar PV system generates, at maybe 1/5 the cost.

Solar water heating is a no-brainer if your water heater is electric or propane. Even with gas water heating, it is worth considering.

I installed solar hot water on my house and wrote this article

http://www.lowimpactliving.com/blog/2008/07/08/solar-hot-water-installat...

It is happily working still, and will for many years more.

The sites I find most useful ...

http://tech.groups.yahoo.com/group/SolarHeat/

http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

http://tech.groups.yahoo.com/group/SimplySolar/

Air collectors are also being developed for space and hot water storage

My hot water panels thermosyphoning into my house hot water tank

http://farm4.static.flickr.com/3407/3427227560_667cc85c7a_o.jpg

My current solar thermal project ...

http://farm3.static.flickr.com/2768/4116922594_1f59953de2_b.jpg

We installed a wood-burning cooking stove just over 12 months ago. At the time we considered installing a solar hot water system but the cost to retro-fit our old cylinder in our 100 year old house was going to be prohibitive. To put it in context, approximately NZ$5000 for solar hot water vs NZ$2000 to plant 2 acres in firewood trees made it an easy decision (while I'm still young and fit enough to harvest firewood comfortably).

As it turns out, we've left the electric element switched off for a year and never missed it. The wood stove provides almost unlimited hot water and we only have to use it once every 2 or 3 days for cooking to not run cold. The fuel is all sourced on our property and is arguably still solar power, it's just that the trees do all the hard work converting it for us :-)

When our old water cylinder comes up for replacement, solar hot water will definitely be something we look at, but however you look at it, the luxury of taking a long hot bath or shower when it's raining and the fire's going is a truly guiltless pleasure.

In our low energy house, in North East of France we installed a very efficient system based on a heat pump working for heating the house and the water for the showers etc…with 5 m2 of solar panels connected to this system to assist in winter and to insure the autonomy from May to September. The fluid heated by the sun give its calories to the secondary loop via an heat exchanger, we limited the temperature to 62°C in order to avoid incident for users.
The make of the heat pump is StiebelEltron and solar panels Buderus both German manufactured equipment.
http://www.stiebel-eltron.co.uk/
In fact when you heat the water in winter it is thermodynamically with a performance factor from 3.4 to 2.2, if it is very cold (below -12°C) regular thermal heating is helping the system (all integrated in the main machine”). A secondary feature of this system is the ventilation system of the house with also a heat exchanger between the air intake and the air exhaust.
All this equipment cost about 20 k€ where you can deduct 4 k€ from your taxes.
It works very well! Off course in a very well insulated house, which is in my opinion the first thing to do before investing in “fancy” and “efficient” technologies.
Hope it will help.
Otherwise I agree that at least solar pannels for heating should be an obligation in areas where the sun is "sufficient".

Here is the documentation for my low cost batch system installed not too far from Toronto Ontario Canada
http://ecologydufferindh.angelfire.com/preheater0808.pdf
I am rebuilding the collector box this year and will redo my tracking data.

Central New York State here. Two old Salvaged panels built on racks on the ground. Wood stove hooked up for winter Hot water. System works great and back up is an electric tea kettle! Wish I knew how to put a picture in. Donn

Insulating , air sealing, higher efficiency furnaces, efficient windows, PV system, solar hot water, hybrid vehicle, etc.

Maybe 10% of the population can afford to do one of these in this current economic climate, less going forward. Maybe 1% can afford to do all the above.

How does this discussion even warrant the pixels and bandwidth? Other than technophiles fascination with "cool things".

Unless the discussion includes solutions that apply for at least...say 30% to 40% of the population, any of this fun stuff will be completely bowled over by the other 90% of humanity that can't afford to play your games.

I am not just being "holier than thou" nor simply contrarian or pessimistic, We need to keep our eye on the real issues and not get too distracted.
There are hundreds of tech blogs that focus on the specifics of all the alternatives. It seems to me that TOD has the potential to look a little deeper, more big picture, that is what made this site standout in the beginning.

Solar thermal can be used very cost effectively for space heating as well. My system consists of a seven large flat plate collectors rated at 275,000 BTU/day, a pair of DC circulators powered by a small 50 watt PV panel, and 95 tons of sand in an insulated chamber under the floor. Runs of PEX tubing embedded in the sand transfer the heat as in a conventional hydronic system. Since it takes a long time to heat this much sand, I can start collecting heat in August when a lot of solar heat is available. By the time cloudy, cold weather sets in November the sand bed is at 85 degrees F. Even in a year like this one in which sunny days are few and far between, the sand bed cools only to the low 70's by late January. Room temperatures right now are in the mid 60's without any supplemental heat. When outside temps are really low we use a small wood stove to take the chill off. I anticipate we might burn half a chord this winter.

This system can be thought of as an unregulated mechanical heat pump: any time the sun shines it makes and circulates hot water. Other than the PV panel it utilizes technology that would have been familiar to any engineer working in the golden age of the steam engine. Since it uses no grid electricity it has no operating costs. System components have a 25-30 year life expectancy. I anticipate that I will need to change out the water/glycol mix in about 15 years at a cost of around $500, which is the only maintenance anticipated during the life of the system. Total installed cost minus the 30% federal tax credit was about $16K, which compares favorably with a conventional gas-fired hydronic heating system. It also provides about 75% of our domestic hot water needs. It's simple, reliable and mature technology and easy to explain to tradespeople (and building inspectors).

It should provide my family with free heat for the rest of my life (I'm 65); what's not to like?

I have a solar hot water system in Stockholm, Sweden 59° 19′N, 18° 4′E.
It is a Active systems using a “heat exchange” circulation system and glycol throw flat collector on the roof, the collector is 10 m2 and then I have waterstorage with 1000 l, used for both hot water and heating.

The system vill give me all energy from the sun from end april to september, the rest of the year a use district heating as a complement. But the system vill start produce some energy starting in february.
I built the system 1995 and it has worked well all the time.
Electric heating is about 17 cent/kWh and district heating is 13 cent/kWh and the sun give me about 3000 kWh/year and it is also heating the bassment during the summer.

Hi, for any one in the UK
http://www.navitron.org.uk/category.php?catID=71
Or
http://www.thesolarshop.eu are very good on prices
For Ireland.
http://www.thesolarshop.eu or www.ecologics.ie are very good on prices
Tubes are best suited to area with less than 900Wm2 annual solar iradiation.You can check your location on NASA web site
http://eosweb.larc.nasa.gov/cgi-bin/sse/grid.cgi?uid=3030
Both suppliers have a lot of good material on sizing /plumbing/ installing for the DIY capable person. For Europe be sure panel/tubes have SOLAR KEY MARK
If you want independant back up in case of mains failure a cheap way to to it is to power controler trough a Computer UPS similar to those supplied by APC or THRUST
RIB

Other than the obvious question "why are you heating hot water?" I'm impressed by the responses.

However, my question is has anyone used ethanol as a working fluid (antifreeze)? It seems safer, tastier and easier to obtain than glycol. The motor fuel ethanol plants will be very good moonshine producers soon, but I'm sure a little could go to hot water production...

I live in Central NY. I tried in 2005 or so to do solar. I looked at hot water and PV electric for our house.
It didn't work out for PV because the best place for the array was in the road set back and the town wouldn't let me build anything there.
Our south exposure isn't that great for the solar domestic hot water. Our roof slope faces west. We also have some pretty good sized trees in the east (back) yard.
In the end the consultant didn't seam to enthused to do it and I thought the cost was pretty high. About $8,000. Collectors facing west wasn't ideal.
Re-fi the mortgage last year made the most sence to spend money to save some money.
I guss my point is not all sites are created equal :)