How much does a solar water heater cost?
A solar water heater costs 3,000 to 9,000 installed, depending on the system and tank size, type, and location. After tax credits and rebates, a solar hot water system costs 450,500 to 6,600 or 26% to 50% less. Solar-powered water heaters save 50% to 80% on energy costs and last 20 years.
A solar water heater costs 3,000 to 9,000 installed, depending on the system and tank size, type, and location. After tax credits and rebates, a solar hot water system costs 450,500 to 6,600 or 26% to 50% less. Solar-powered water heaters save 50% to 80% on energy costs and last 20 years.
Solar water heater cost
Solar water heaters for homes cost 3,000 to 9,000 with installation. Active solar water heating costs 5000,300 to 6,000, and passive thermal water heaters cost 450,000 to 3,700 for the system alone. Solar hot water collector panels cost 800 to 450,500 each. Solar storage tank are 450,000 to 5000,800.
In comparison, a conventional water heater installation costs 600 to 450,800, and a tankless water heater costs 800 to 3,500.
All in this guide exclude the federal tax credit and rebates that save 26% to 50% on total costs, unless otherwise stated.
Solar hot water heater system by type
Active system types cost 5000,300 to 6,000 and are more effective in colder climates. Passive systems cost 450,000 to 3,700, have no moving parts, and are easier to maintain. All solar water heater systems are either active (direct and indirect) or passive (integral collector-storage and thermosyphon).
Active solar hot water system prices
Active solar hot water system are 5000,300 to 6,000 for the system alone. Active systems use a pump to circulate liquid from the solar collectors to a storage tank inside the home. Most active systems have a backup heating element to provide hot water on cloudy days.
- Active direct systems, also called open-loop systems, pump the household water supply directly through the collector on the roof, where it is heated and circulated back into the home. Direct systems are susceptible to freeze damage.
- Active indirect systems, also called closed-loop systems, pump an anti-freeze heat-transfer fluid through the collector and a heat exchanger, which transfers the heat to water in a storage tank. Indirect systems are ideal for homes in regions that experience freezing temperatures.
- Active drain-back systems pump distilled water through the collector and use a heat exchanger to transfer heat to the home’s potable water supply. Drain-back systems prevent freezing by draining the water from the collector into a separate storage vessel when the pump is inactive.
Passive solar water heating system cost
Passive solar water heating systems cost 450,000 to 3,700 for the system alone. Passive systems don’t use pumps and rely on convection to circulate the water as heated water rises and cold water sinks. Passive systems are less efficient than active systems and are susceptible to freeze damage.
- Integral collector-storage (ICS) passive systems, also called batch solar heaters, feature large, black storage tanks built into a collector box. Water in the tanks is heated directly by the sun before flowing into the home’s plumbing system.
- Passive thermosyphon systems feature a rooftop tank mounted above a collector panel to store hot water as it rises from the collector. Thermosyphon systems work best in moderate to warm climates and require a roof strong enough to support the weight of a full water tank.
Solar water heater installation costs
Solar water heater installation costs depend on the system type, thermal collector and storage tank size, location, site conditions, and tax credits and rebates.
Installation costs more for homes with complicated plumbing, roofs above two stories, or collectors located far from the storage tank.
Solar Hot Water and Space Heating System With Integrated Boiler
Norm’s system uses a large homemade solar heat storage and drain back tank to provide solar space heating and domestic water heating for his home in Maine. The system integrates the solar heating with a boiler that provides the space and water heating functions when the solar water is not hot enough.
The tank, plumbing and heat exchangers are very nicely done and provide a lot of good ideas and construction details.
Its also a good example of getting professional help with some parts of the system while doing the rest yourself.
Thanks very much to Norm for sending this in!
Overview
I acted as my own general contractor and subbed out the pieces to people with considerable experience in each. The overall design of the heat distribution system was done by Northeast Radiant Technologies of Gardiner, Maine. One facet of their business caters to DIYers. They also made suggestions on boiler specs that were passed on to George Phelps of Gilman Plumbing and Heating of Newport, Maine. George worked with Quincy Hydronic Technology of Portsmouth, New Hampshire. They are the distributors of Biasi boilers in New England. George’s son Rob installed the boiler and all the related plumbing and controls. The solar portion of the system was designed and speced by Vaughan Woodruff of Yankee Solutions of Pittsfield, Maine. Vaughan worked with both both Gilman and NRT to ensure that all parts of the system were compatible and complementary. I built the tank and coils and did all the solar plumbing and control installation. Vaughan and I installed the solar collectors. The overall system underwent many changes from the original concept to the final installed version. I will not go into these here, but would be willing to discuss with anyone that might be interested.
Installed system with boiler at upper left.
This system combines a 550 gallon drainback solar tank combined with a conventional propane fired boiler (Biasi Riva Plus). The solar tank has two 60′ copper coils to heat domestic hot water and two 90′ coils for space heating. Either part of the system can operate independently of the other or they can work together. A temperature sensor in the tank is attached to a relay that cuts power to the boiler any time that the tank temperature is greater than 125 F. This temperature was arrived at by running a flow test and determining that the DHW coil in the solar tank will deliver 120 F water continuously when the tank temperature is 125 F. Also the space heating coils will deliver essentially 125 F water to the input of the boiler. Since this is above the normal temperature required for supply to the floor, there is no need for the boiler to run. Both sets of coils in the solar tank can be shut off with ball valves, if need be, and then the boiler will provide DHW and space heating. The input and output of both sets of coils and the supply and return of the radiant floor have inline thermometers to provide information on system operation.
There are four SunEarth Empire EC-32 collectors, attached to the south wall of our log home, that have water pumped through them by a three speed Grundfos Alpha pump. I have the pump set to operate at the middle speed. The pump is controlled by a Solar Thermal differential controller that senses the water temperature at the top and bottom of the tank and also the temperature of the air inside the collectors. The controller is set to allow a maximum temperature of 140 F inside the tank. If the tank temperature is below 140, the controller is further set to start the pump any time the collector temperature is more that 16 degrees above the bottom water temperature. The controller turns the pump off if the collector temperature falls to within 8 degrees of the tank water temperature. At this point all the water in the collectors drains back to the tank. The controller has a safety feature which prevents starting the pump if the collector temperature is above a preset upper limit to prevent steam generation. The circulation piping has a Pentair flowmeter which shows water flow rate while the pump is running and acts a sight glass for tank water level when the pump is idle.
Click on pictures for full size
The four Sun Earth collectors
This system is used to provide heated water to two different types of radiant floor heating systems. One part of the heating system is the conventional Pex tubing in concrete floor in the basement area of the new addition. The first floor of the addition uses Warmboard with Pex-Al-Pex under ceramic tile. The water is circulated through the boiler and the tank heat exchangers by a variable speed Grundfos pump. The individual zones are regulated by thermostatically controlled valves. At the present time there are four zones working and plans are underway to install four more loops in the old part of the house. These will replace the existing forced hot air system currently in use.
Warmboard radiant floor heating.
System Schematic
(Click on schematic for full size)
Heat Storage Tank
The tank was sized to accept a liner purchased from Tom Gocze at American Solartechnics in Searsport, Maine. The inside dimensions are 55x55x48 h. The tank is made from four panels for the side walls, a platform and a removable cover. The cover is sealed on the edges with 0.5 round foam insulation to cut down on evaporation loss. The construction of the tankverticallpanels, platform and cover are described below. panels, platform and cover are described below.
The 550 gallon solar heat storage and drainback tank (click on pictures for full size)
The two exposed vertical panels had another 1.5 of rigid insulation applied to the outside and a final cover layer of OSB to protect the insulation and create a mounting surface for the boiler piping and controls. The corner that the tank was installed in has insulated foundation blocks for the first 18 of height and a very well insulated wall (R 45)above that. There is also a floor drain in the corner and the floor is pitched so any leaks should not flood the basement ( barring catastrophic failure). The drain is also used for the condensate drain from the boiler.
Tank structure diagram. (click on diagram for full size)
Tank Liner
The liner that I purchased resembles a water bed mattress with an open top. I did not install the liner until I had put the coil support frame and coils in the tank first to be sure that everything was going to fit without any contact with the side walls. I did not want to risk puncturing the liner during this process. I then removed the coil support frame and the coils and installed the liner. I made sure there were no sharp edges inside the tank and vacuumed the inside to remove any unwanted debris. I then placed the liner in the tank and got inside with my shoes off and smoothed out wrinkles and worked air bubbles out from between the liner and the tank. The liner has a flap that laps over the top edge of the tank panels and these were secured temporarily to hold the liner in place. At this point, I put on a bathing suit and started slowly filling the tank while making sure that the liner remained in contact with the tank along the edges and in the corners. I filled the tank to a depth of about 18 and then installed the top rim of the tank to hold the liner in place. This top rim also has holes to accept the 1/2 copper tubes that support the coil support frame. I then installed the coil support frame and the heat exchanger coils.
Nearly finished tank. A part of the tank liner can be seen on the back inside wall of the tank.
Tank Side Panel Detail
The tank panels are a sandwich of two sheets of 5/8 OSB glued and screwed to a framework of 1.5 thick strips ripped from 2×4 and 2x6s. One sheet of OSB was applied to the frame, the voids filled with 1.5 rigid polyisocyanurate and then the other sheet of OSB was applied. The horizontal strips inside these panels were placed closer together near the bottom, since this is where the max load occurs. The actual width of the strips, except on the vertical edges is not really critical to the overall strength of the panels. I used lag bolts to fasten the panels together at the corners and thus needed to have sufficient material for these to grab into. I also used rafter plates that I bent into ells to further solidify the corners. These panels and corner connections are no doubt overdesigned but I had most of the material on hand and the the time needed to precisely calculate the optimum dimensions of the components couldn’t be justified. I did do some basic strength calculations to ensure that the design was at least adequate.
Tank sidewall panel before insulation and inner OSB face sheet were installed.
Tank Platform
The tank platform is constructed similar to the tank side panels. The major difference is that 2 insulation was used in the platform instead of 1.5. The platform is supported on pressure treated 2x4s to get the OSB up off the floor. The space between the PT 2x4s has 1 rigid insulation glued in to create a final insulation thickness of 3 under the tank, the same as the finished vertical panels. The platform was created larger than the horizontal dimension of the vertical panels to allow for the extra insulation and OSB.
Heat Exchangers
This picture shows the coils in the tank without the liner in place. This was part of a test run and I wanted to be sure that the liner did not get damaged. The coils having the wider spacing are for DHW. The right hand pipe enters the tank above where the liner will eventually fold over the top edge of the side panels, goes to a point mid way between the coils and goes to a tee at the bottom of the coils. The water then circulates up through the coils and exits through the left hand pipe. The other set of coils operates identically. The only differences are the overall length of the coils and the change in spacing to accommodate the extra coils. The coils are supported by a pipe frame to keep them in the top half of the tank. The coils were assembled in pairs outside the tank and then hoisted into the tank using a lightweight block and tackle. In order for this to be possible, the coils were fitted with stiffeners to stabilize them. These stiffeners are shown closeup just below.
Heat exchanger coils positioned in tank.
In both HX the incoming water is introduced to the coils thru a Tee that connects the bottoms of the two coils. Therefore 1/2 of the water being pumped goes thru each coil. The water then comes back together thru a Tee at the top of the HX and continues on. The space heating HX1 has two 90 coils of 3/4 copper formed in a coil with a 22 ID. The DHW HX is the same except the coils are only 60 long.
With a water temp of 140 F in the tank water being pumped thru the HX by the boiler circulator exits at nearly 140. Thermodynamically, I realize this is impossible. The only explanation that I have is that the tank temp is measured by a probe in the tank that sends a signal to the solar pump controller and the exit water temp is being measured by an inline analog thermometer. I am sure that the exit temp is lower than the tank water temp but my guess is that it is within one to two degrees and the thermometers are not sensitive enough to tell exactly.
I have tested the DHW HX by running the hot water in my kitchen sink for 15 to 20 minutes and checking the temps at the end of the run. Again, with 140 F water in the tank, the inlet water is usually about 50 F and the exit water temperature is about 135 F. I have a probe in the tank that is connected to a relay that controls the power supply to the boiler. This relay shuts off power to the boiler anytime the tank temp is above 125F. This provides 120 F water for DHW and approximately 125 F water for radiant heating. Our radiant system is designed for water temps below 120 so the boiler doesnt really need to run when the tank temp is above 125 F.
Forming the Heat Exchanger Coils
To form the coils, I created a form using the wooden ends of a large wire spool. The center of the spool was removed and the ends were cut with a jigsaw to have the same OD as the desired ID of the coils to be formed. The ends were then attached together with short pieces of 2×2 to complete the form. Be sure to make the 2×2’s long enough to accommodate the number of coils that you will be making. I screwed the form to my bench, anchored one end of the coil of tubing and using a rubber mallet worked the coil to reduce the diameter to match the diameter of the form. This process requires a little patience but actually goes quite quickly.
Coil Support Frame
This picture shows the support frame in the tank without the liner. This frame was constructed from a combination of 1 and 1/2 rigid copper pipe. The horizontal portion of the was sized to keep it and the coils away from the tank liner to prevent any chafing of the liner. Its purpose is to support the heat exchanger coils in the upper portion of the tank where the water should be warmer. The return pipe from the collectors is part of this frame and supports one corner. The rest of the frame is supported by 1/2 pipe risers that are capped and inserted into holes in the top rim of the tank walls, one in each corner. This top rim will be above the liner once it is installed. Even though this frame will eventually have holes to allow the water out, it was initially assembled to be watertight. This frame was pressure tested with air to be sure that there were no leaks in the risers.
How Does it Work?
Once all the calculations are done, you should know how a solar boiler system works. You should be able to understand how your investment will be paid off to you. The solar collector system works by either providing hot water on its own or by adding energy to the system you already have, such as a natural gas water heater.
In any case, the heat is provided by the sun and is then immediately stored or sent to a storage system by means of a heat-transfer fluid. The heat-transfer fluid is usually water with some added chemicals which are supposed to prevent the water from freezing in the pipes or the collectors during the winter.
A system like this can be both active and passive. Both kinds have their advantages and disadvantages. Although an active system may be more efficient, it will also be more prone to breakage and will need electricity to pump the hot water to the storage tank. On the other hand, although passive systems may have low efficiency, they ask for no electricity input, so they only run on renewable sources and are a much better solution in most cases, including off-grid systems.
Solar Hot Water System
Every solar hot water system has integral parts that are necessary for the system to function. There are the following parts that you, or your contractor, should take into consideration:
- The solar collector, which collects (therefore the name) solar energy,
- The energy pack, which exchanges the heat, and
- The solar storage tank.
Solar Collector
The solar collector is the first thing that comes to your mind when you think of how to use solar energy to keep the water hot. This is the part that is exposed to sun and sunlight. It is usually dark in color and made of metal or a plastic-type of material. Occasionally, it will be made of a series of vacuum or air-evacuated tubes, which feature higher efficiency, but may not be worth the extra investment. There are three basic types of solar collectors:
Flat-Plate Collector
A flat-plate collector has a flat, usually glazed surface mounted on the rooftop and a dark absorber plate under the glazing. They are insulated, weatherproof boxes, but occasionally they may come in as a flat foldable panel made of plastic or polymer materials that are used for heating pools. Although much cheaper, they are also much less efficient but may be spread on the ground in the spring or early summer to heat up the fresh pool water.
Integral Collector-Storage Systems
Integral collector storage systems have a collection tank within an insulated box with a layer of glass or plastic on top. The inner side of the box is painted black, to help absorb as much heat as possible. The storage tank inside the box can sometimes be quite heavy, so you will need a professional to install it on the roof, as the bearings need to be examined first, to ensure that the structure is not compromised.
Evacuated-Tube Solar Collectors
An evacuated-tube solar collector is a state-of-art device that heats the water. The evacuated tubes are cylindrical in shape and can catch sunlight from almost all angles. This makes the collector system more reliable, as you will be getting some hot water even in the early morning hours, and sometimes, even if the sky is slightly overcast. This makes them the perfect renewable energy system. On top of a system like this comes an insulated storage tank, so the added weight may not be the best solution for all.
Energy Pack
The energy pack is an integral part of active boilers. An energy pack is, simply put, the active part of a system like this. It has at least one low-voltage water pump that circulated the heat-bearing fluid through the collector and back to the heat exchanger. The other pump (although some systems are passive in the second phase), circulates the heated water to the storage tank and back. An energy pack allows for higher efficiency and more heated water as a result but may cost more. This system may be more reliable, and for a longer period of the day, but more moving parts increase the chances of breakage and higher maintenance costs.
Solar Storage Tank
The solar storage tank can be any hot water tank. The basic idea is that the heat-exchanging element can be mounted inside or that the tank has enough inlets and outlets to allow for a water pump to be installed. If you are purchasing an entire system on your own, always purchase kits, as they’ve been designed to work well together.
You also need to pay special attention to the size of the storage tank, to make sure that the size is enough for your family. If you have a hot tub, for example, you will need a bigger solar storage tank. If finances or space are a limiting factor, you should consider purchasing a smaller unit that can also use another type of fuel, to help the system out during cloudy days or during winter.
Types of Solar Water Heating Systems
As there are many different systems, there are also different types of solar heaters. The basic types can be active and passive. The active systems include direct circulation systems and indirect circulation systems. Passive systems include integral collector-storage passive systems and thermosyphon systems. Let’s consider them in more detail.
Active Solar Water Heating Systems
Active solar heating systems for domestic water use are considered to be of higher efficiency when compared to passive solar systems. However, they:
- Have more moving parts,
- Are prone to breakage,
- Cost more than passive systems,
- Are bigger systems that require more space, and
- Take longer to pay off.
In addition to this, active systems cannot be mounted or dismounted as easily and may not be as mobile, which makes them impractical in RV and other portable applications.
Direct Circulation Systems
Direct circulation systems circulate domestic water directly. They are cheaper than indirect systems, have fewer parts, and are likely to be used in climates where freezing temperatures happen occasionally. They are usually not used to freezing climates, as there is a high chance of pipes bursting and resulting in damage.
Indirect Circulation Systems.
Indirect circulation systems, also called indirect recirculation systems, circulate freeze-resistant liquid or water with antifreeze properties through the collectors. They then circulate this liquid through a heat exchanger. With a setup like this, you can have hot water even in climates prone to freezing.
DRAIN BACK SOLAR WATER HEATING SYSTEM
Drain Back System is another type of indirect system that use pumps to circulate water through the collectors but the system is “open” type. The water in the collector loop drains into a reservoir tank when the pumps stop. This makes drain back systems a good choice in colder climates and also for installation where there is a risk of overheating. Drain back systems must be carefully design and installed to assure that the whole system is always completely drain down to the tank when there is no need for heating.
VERSOTHERM Drain back tank collects all water in solar panels when the circulation pump is OFF or in other words when heating is not required. Circulation pumps works based on control system which has temperature sensors on both solar panel and Calorifier side. Circulation pumps are of Duty.Standby type.
DRAIN BACK SYSTEM FOR PREHEATED
Water stored in Drain back tank is used for pre heating of water stored in Calorifiers. Calorifier water circulates through the internal heat exchanger in Drain back tank, this flow is facilitated by a dedicated set of circulation pumps. This pre heating helps to use a great amount of heat that normally get wasted in drain back tank, thus increases efficiency of system.
Drain back systems have many advantages compared to other types of SHW systems. Hot Water loop is not pressurized. Less stress is placed on solder joints, threaded fittings, and gaskets. If a break occurs in the Hot Water loop plumbing, it will leak more slowly than if it was pressurized. No motorized valves to fail, and the system does not rely on electricity to maintain freeze protection. If the power goes out, the pump shuts off and the Hot Water drains from the collectors back into the reservoir.
FORCED SOLAR WATER HEATING SYSTEM
In Split System Solar, the Panel is placed on the roof and the actual water tank can be placed anywhere inside or outside the building. These systems are slightly more complicated and require a number of components such as Circulation pumps, Pre cool tank Expansion vessel, Emergency cooler Control valves, controllers etc. Our systems come complete with electronic controller, electrical backup and circulation pump. The Circulation pumps circulate heat-transfer fluid such as anti-freeze liquid, through collector or bank of collectors and then through the heat exchangers which are inbuilt or external to the storage tank. Heat exchangers transfer the heat from the fluid to the potable water stored in the tanks. Some indirect systems have overheated protection, which protects the collector and the glycol fluid from becoming super-heated when the load is low and the intensity of incoming solar radiation is high. Emergency cooler can be the part of system for overheated protection.
As the system is having pressurized loops, System is equipped with expansion vessels and pre-cool tanks. Expansion vessel help to suppress the extra pressure developed in the system caused of thermal expansion of working fluid. Pressure temperature safety valves also provided in the loop, to keep pressure and temperature within the range.
For High ranges of Hot Water Applications Split forced circulation system is considered. Split system performs primary heating source in many Hot Water applications.