Solar Heating System
In just one second, the Sun gives off 13 million times the energy that is generated by all the electricity consumed in one year in the United States. Only one millionth of the Sun’s energy reaches Earth, but this scant amount would be more than sufficient to meet the energy requirements of our entire planet. The relative difficulty in extracting energy from the Sun, when compared to systems that derive energy from fossil fuels or nuclear power, has hindered its development as a widespread source of energy. On a smaller scale and in many experimental projects, however, solar energy has proven highly effective in producing both electricity and heat.
Solar energy was first explored for electrical purposes in the 1950s, when the need for continuous electric power generation on space satellites spawned the development of a solar cell in the Bell Telephone Laboratories of the United States. Even today, though, the best silicon solar cell converts sunlight to electric power with only 18% efficiency. Still, experiments have utilized sun-generated electricity with great success. One highly visible project focusing on solar power is the annual international solar-powered automobile race.
Solar energy has proven more effective and has been more widely utilized for both water and space heating and cooling systems. As a water heater, solar energy is most commonly used to heat swimming pools. For space heating, two main types of systems are used. A passive solar heating system admits solar energy directly into a building through large Windows facing south (in the northern hemisphere) and directly heats the space within (this is known as direct gain and is also referred to as the greenhouse effect) or through a wall or roof that absorbs the solar radiation, stores the resulting heat, and transfers the heat into the building (this is known as indirect gain). A passive system may also utilize an absorber and storage components (such as a rock bed) that are not a part of the building, but are contained in their own separate chamber. This is known as an isolated-gain system.
Active solar heating systems use water or air to transport heat from collectors mounted on the south-facing side (again, in the northern hemisphere) of a building’s roof to rock beds or water tanks. The stored heat may either be allowed into a room directly when utilizing rock beds and air as the transfer fluid, or through fan-coil units when the solar energy first heats water. The heat is then transferred through the coils to heat the air. Cooling systems are also divided into passive and active systems which utilize night air and condensation to cool the air in a building.
Different types of solar collector panels may be used and suited to the type of facility being heated or cooled. A flat-plate collector, a large, flat box with a glass top and a heat-absorbent black bottom containing pipes that run parallel to the top and bottom, is best suited to domestic use. A concentrating collector, made of reflecting materials and shaped like a trough or bowl, is best suited to industrial use.
The sun has served as source of heat since the beginning of time, but the earliest documented
use of a human-constructed solar collection system dates back to 1776 when Swiss scientist Horace de Saussure developed a rudimentary collector commonly referred to as a hot box. Astronomer Sir John Herschel used hot boxes to cook food during an expedition to Africa in the 1830s, and the use of solar thermal energy for cooking and water distillation purposes subsequently became common in certain parts of Africa.
Early American pioneers of the late 1800s used black pots and pans to heat up water as they traveled during the day, thus popularizing the use of solar energy to heat water. The idea was put into widespread use in areas of the country which otherwise had to import fuel for water heating. For example, in 1897 nearly 30% of the houses in Pasadena, Califomia, utilized solar water heaters.
Solar energy continued to be used moderately throughout the next century, but leapt in popularity during the energy and oil crisis of the 1970s. Use of solar energy tapered off as the energy crisis waned, but has risen again in popularity in the 1990s as populations become increasingly aware of the environmental and public health hazards caused by the burning of fossil fuels and the use of nuclear power.
Because there are many types of solar heating systems, there is a wide variety of raw materials that may be used in their manufacture. This entry will FOCUS on a basic residential passive system and a basic residential active system.
A passive solar heating system requires a black flat-plate collector panel made of a steel absorber plate covered with two sheets of glass and an insulating pad made of fiber-glass insulation or polyurethane foam with an aluminum foil facing, which acts as a moisture barrier. The system is contained in a shallow box made of wood, galvanized steel, or aluminum. The system also typically requires a heat storage bin, containing dry pebbles or rocks. This unit stores heat when a building is sufficiently heated. In addition, the system requires a differential thermostat, an electronic system which allows manual control of the heat levels and, thus, room temperatures, and an air-handling module consisting of connecting ducts, air filters, a blower, and automatic dampers.
An active residential solar heating system utilizing water as the storage agent requires a flat-plate collector constructed of one or two sheets of glass or transparent plastic with black metal tubing and an insulation pad made of fiberglass board or a similar insulating material. The system also requires water pumps, a storage tank, heat exchanging coils, an auxiliary heater, a fan, filters, and a control valve. If rocks are used as the storage material, an insulated bin
All solar heating systems utilize caulking, aluminum siding, and closure strips, most likely made of rubber, paint, and wood.
The Manufacturing Process
- 1 Flat plate collectors are installed on either a pitched roof or vertical walls by installing shallow, sheet metal manifold pans, which resemble large baking pans, at each end of the collectors and fastening the pans to the rafters of the roof or wall. Caulking is then applied liberally around the upper edge of the manifold pans. Sheathing is next attached to the roof or wall, and all seams are caulked. Manifold slots are cut in the sheathing, and blocking is fastened around the perimeter of the sheathing.
- 2 The absorber plate is installed over the sheathing, extending to the outer manifold blocking. The ends are sealed with end closure strips, typically made of rubber and caulking. The top and bottom edges are also caulked.
- 3 Battens are fastened to the absorber O plate, and a glazing system consisting of a single layer of glass on a roof or a double layer of glass on a wall is attached.
- 4 Aluminum glazing bars are installed around the perimeter of the collector.
Air handling and control system
- 5 In a passive system, the air handling system consists solely of ductwork installed between the collector and the living space, as well as a fan and a manual control to activate the fan. An isolated gain system would also include a separate storage chamber and ductwork leading to and from the chamber.
- 6 In an active system, a storage bin holding rocks or water is required to store excess heat. Ductwork with on-off dampers are installed running from the collector to the house, the collector to the storage bin, and the storage bin to the house. Two fans are installed.
- 7 A rock storage system is constructed of an insulated bin filled with small rocks 1-5 in (2.5-12.7 cm) in width. Sufficient space is allowed between the rocks to facilitate the blowing of air through the duct connections at either end of the bin.
- 8 A water storage system is similar to the rock storage system, using water rather than rocks.
For a residential solar heating system, the fit of the end closures and adequacy of the caulking on the collectors may be tested using a smoke bomb to detect any leaks. The smoke test is conducted prior to glazing.
As more prototypes of solar-heated and solar-powered living and commercial units are developed, this source of energy shows serious signs of growing into source of heat and electricity that is more than experimental. Environmental and natural resource groups, as well as and often in cooperation with the United States Department of Energy and several international organizations, continue to push for a more widespread reliance on solar heat and power as well as continually develop new and innovative uses for this source of energy. While the work inside the Department of Energy’s Solar Energy Research Facility focuses on photovoltaic power, the building itself stands as a testament to the success of solar energy. The building’s innovative, window-laden, stairstep-like design allows for direct sun lighting and heating and stands as an example of how successful the reliance on solar energy can be—and how prevalent such reliance could become in the future.
The American Solar Energy Society demonstrates the practicality of solar energy in its annual solar home tours. The organization also keeps its members posted on legislative developments regarding solar energy matters. In July 1996, for instance, the organization was active in lobbying for the passage of renewable energy funding legislation. While no such legislation has been enacted to date, introduction of such bills indicates an interest in solar energy issues among at least some members of Congress. The International Solar Energy Society is concerned with similar issues on a global level, and works for a greater reliance on solar energy worldwide.
Where to Learn
American Solar Energy Society. June 3, 1997. http://www.csn.net/solar/ (July 14, 1997).
Center for Renewable Energy and Sustainable Technology. http://solstice.crest.org (July 14, 1997).
International Solar Energy Society. http://www.ises.org (July 14, 1997).
Passive Solar Industries Council. http://www.psic.org (July 14, 1997).
Pros and Cons of Solar Water Heaters
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If you’re thinking about harnessing the power of the sun, you’ll want to consider the pros and cons of a solar water heater. It’s a good way to test the water with utilizing green energy without diving-in with 100% of your electrical.
This article will give your the advantages and disadvantages of moving to a solar water heating system to help you make an educated decision. If you’re a DIY kind of person, you may want to consider building your own system. Check out our article here.
Advantages of Solar Water Heaters
Do you like the thought of free energy? Well a solar water heater will allow you to harness the energy from the sun and reduce your electrical bill as much as 50% for electric water heaters.
If you live in an area where there’s plenty of sunshine, such as Arizona, then your water heating bill could drop as much as 90%!
Carbon Footprint Reduction
Heating your water with a solar water heater will not only reduce your electric or gas bill, it’ll also reduce your carbon footprint.
Traditional gas and electric water heaters use and release natural gas or fossil fuels into the atmosphere. Using a solar water heater does neither. Which means you get to save money while helping save the environment. How cool is that!
Fewer Solar Panels
If you want to take advantage of solar energy, but aren’t thrilled with the idea of covering your entire roof with solar panels. You can make a huge impact on reducing your energy bills by simply switching your water heating to solar.
One to three solar panels is all it takes to power the average household solar water heater, and with fewer solar panels, the installation costs will also be less.
Increase Home Value
Adding a solar water heating system, or any green energy feature, will increase your home’s value.
and more buyers are looking for home’s with energy-saving features.
With government rebates and tax credits you’ll be able to offset the cost of purchasing and installing your solar hot water system.
Check your state for any incentives they may offer, and for federal incentives, you can check here.
Hot Water Always Available
Even if you live in an area without a lot of sun, you can still take advantage of a solar water heater.
These systems have an electric or gas back-up system for those days when the sun doesn’t come out. You’ll have the best of both worlds, reliable hot water regardless of the weather, yet still be able to reduce your water heating bill.
Disadvantages of Solar Water Heaters
We’re not going to lie, adding a solar water heater to your home isn’t cheap. Although every install is unique, 9,000 is a good rough estimate.
The good news is, you may be able to qualify for tax credits or rebates to help offset the initial costs. Learn more about federal programs here, and there may even be incentives at your state level.
Adding a solar water heating system to your home is truly an investment, but keep in mind that once they are installed, and if they are properly maintained, it’s not uncommon to see these systems last over 20 years!
Climate Impacts Performance
Even though solar panels are able to generate heat on cloudy days, they typically are not as efficient.
If you live in a state that has less sunshine during the winter months, your system won’t deliver the same financial benefits as a solar water heater owner who lives in Arizona or another state with plenty of sunshine.
But you won’t need to worry about cold showers, because solar water heating systems include either a gas or electric back-up water heater which will prevent you from running out of hot water when the sun is hidden deep behind the clouds.
Mounted on Roof
Not only will your solar water heater panels need to be mounted on the roof, but you’ll need to ensure they are facing the right direction to maximize their performance. They’ll also need to be in an area where there’s little to no shade from tall buildings or trees.
In addition, older homes may not be able to handle the weight of the system and require the roof to be reinforced.
It’s a good idea to talk with a professional prior to purchasing a system. By stopping by and looking at your property, an installer will be able to determine if a solar water heating system is right for you and your home.
All water heaters require maintenance. Tanks need to be flushed and valves and connections need to be inspected.
But when it comes to solar systems you may have a difficult time finding someone qualified to do the maintenance. Keep in mind that this may change as more and more homeowners are moving towards green energy.
Solar Thermal Hot Water Systems and Individual Components
Stiebel Eltron has been designing solar thermal systems for 40 years. Because every installation is different, we have a full line of SOLkits, mounting hardware, and the individual components necessary for solar thermal installations. We are committed to making and supplying the best solar thermal components available. We’ve been at the forefront of water heating technology for over 95 years. As a leader in the field we have no intention of standing still.
Why Solar Thermal?
The cost to make hot water is the largest utility expense for a household. The average is about 20% of household energy for just domestic hot water (cooking, cleaning, bathing). This jumps to about 50% if hot water is also used for heating. It makes sense to save as much as possible on hot water, which is exactly what solar thermal can do.
Solar thermal has been used to capture the power of the sun and turn it into hot water for decades before solar photovoltaic (PV) became a possibility. Solar thermal is 3 to 5 times as effective in capturing the sun’s power as PV. Solar thermal can save up to 75% off water heating bills. It reduces carbon footprint and increases the property value of a home.
Federal tax credits are in place for 30% of the installed cost of a solar thermal system. State rebates and incentives, as well as local utility incentives, exist in many parts of the country.
How a Solar Thermal System Works
Collectors absorb the sun’s heat energy and transfer it to a heat transfer fluid in the system. A pump moves the hot fluid to a domestic water tank where the heat is transferred to the water through a heat exchanger. The now cool heat transfer fluid circulates back to the collector to gather more heat.
Stiebel Eltron has been designing and manufacturing solar thermal components for 40 years. Like all of Stiebel Eltron’s products, our solar components are carefully engineered. They are designed to work both individually and system-wide to bring you the best in performance and reliability.
Explore a Live Solar Thermal Installation
You can interact with a live Stiebel Eltron solar thermal installation in real-time to learn more about how our system functions.
Systems to Meet Any Needs
Solar thermal systems can be tailored to meet just about any need or existing mechanical situation. The diagrams show three common solar thermal installations. Many components of a solar thermal system are universal to all systems.
Solar Thermal Collectors Absorbs energy from the sun, converting it into heat.
Heat Transfer Fluid A propylene glycol food- and pharmaceutical-grade fluid that holds and transfers heat from the collectors to the tank. The heat transfer fluid is freeze-proof for cold nights.
Pump Station Moves the heat transfer fluid around the system.
DHW Storage Tank The internal heat exchanger transfers the heat from the heat transfer fluid to the domestic hot water the tank holds. A backup heating element keeps the tank hot when the sun isn’t shining.
Controller An electronic device that controls the operation of the pump and the safety of the system.
Backup Options A backup system is used to add additional heat to the household hot water if necessary. This situation can happen, for instance, on a very cloudy day if the solar system can not make enough hot water to satisfy the demand or make it hot enough. The Stiebel Eltron SB E tanks in SOLkits have integral electric backup, but other possible solutions include Stiebel Eltron Tempra ® tankless electric water heaters or existing site-specific backup systems.
SOLkit Water Heating Packages
Stiebel Eltron SOLkits highlight our 40 years of solar thermal experience by combining the best solar components into complete packages. SOLkits come in 1, 2, or 3 panel sizes in up-roof configuration, and 2 or 3 panel sizes across the roof. Selection of the correct kit depends on family size, domestic hot water needs, and space heating needs if required. Our expert service representatives are available by phone or email for assistance and recommendations. Kits come complete with recommended pump station, controller, and tank. A rack kit, and the line set for a particular installation, completes the package, supplying every component needed. Our components are designed for maximum compatibility, ease of installation, and reliability.
Flat Plate Collectors
Stiebel Eltron SOL 27 Premium is a highly efficient solar thermal collector, among the top 10 collectors measured for output by the SRCC. The net absorber surface of over 25 square feet results in a maximum output of 31,300 btu/day per panel (SRCC clear day rating). The SOL 27 Premium features a highly selective absorber coating, low-iron, tempered solar glazing, and very effective insulation around the absorber plate. The internal fluid tubes are copper and the absorber plate is aluminum. The low 3˝ profile of the SOL 27 makes it visually less obtrusive and able to accommodate a variety of architectural and engineering needs.
SOL 27 Premium collectors are available in both Standard (Vertical) and Wide (Horizontal) configurations. Manufacturing in the US for our collectors and racking systems also means we can custom-anodize collector frames and racks to meet specific architectural color requirements.
Evacuated Tube Collectors
Stiebel Eltron’s S-Power solar collectors are engineered and made in Germany. They are three to five times more effective at capturing solar power than photovoltaic (PV) systems. Their latest-technology copper absorber plates are sealed inside single-walled, proprietary glass tubes with an uncompromising vacuum seal. Ideal for conditions where the outside temperatures are low and the demands for thermal energy are high, they are particularly well suited for combination systems where hot water, space heating, and air conditioning are required.
Stiebel Eltron SB 300 400 E DHW tanks are made in our factory in Slovakia. They come in both 80 gallon (300 l) and 110 gallon (400 l) sizes and can serve as a dedicated high-capacity solar storage tank in both residential and commercial installations.
Stiebel Eltron tanks and heat exchangers are made of heavy gauge steel. All surfaces in contact with domestic hot water receive a thick porcelain enamel coating after shot-peening to clean the steel surface. In addition, vessel exteriors receive a light porcelain coating. Two inches of urethane foam insulation ensures that hot water stays hot, and standby heat loss is minimized. Stiebel Eltron SBB tanks are equipped with large sacrificial anodes with wear indicator and an extra-large clean-out port for ease of maintenance.
SB 300 and 400 E storage tanks are equipped with a 3 kW electric heating element to back up the solar production. This heating element is sheathed in a steel cylinder inside the tank, and can be removed and replaced without needing to depressurize and drain the tank.
Auxiliary ports allow for additional installation applications, including boiler backup, split heat pumps, and hydronic applications.
Stiebel Eltron also sells German-made single and dual coil storage tanks without the electric backups.
Stiebel Eltron Controller
The SOM 6 Plus controller is used for all Stiebel Eltron standard solar thermal systems. The controller is equipped with an illuminated system-monitoring display. Adjustment and control of the solar system can be easily carried out through the user-friendly pictograph display. The SOM 6 Plus features 4 temperature sensors, a solar operating hours counter, variable pump speed control, vacation mode, and an industry-standard resol vBus ®.
Other Stiebel Eltron controllers are available for larger residential and commercial systems, including complex commercial systems.
Stiebel Eltron Pump Stations are specially designed for closed loop solar systems. The 3-speed Wilo circulator pump is designed to perfectly integrate with our SOM 6 Plus controller. Pump station piping is high grade brass. Pump stations come preassembled with a steel wall mounting bracket and feature 2 drain valves, brass check valves to prevent thermo-siphoning, integrated flow meter, and include fittings for tank mount as well as NPT adapters. The pump station can be completely isolated from the system, so no draining is necessary during servicing.
Stiebel Eltron’s optional Solarwave DL2 datalogger gives owners remote access via the internet to their solar thermal system. Dashboards are designed for both owners and installers, and include a diagram view for virtual inspection of the system. Installers can manage and control systems remotely and set optional email alarms for notification of performance issues. Remote access reduces on-site cost for service contracts.
Stiebel Eltron mounting systems are made in the U.S. from extruded aluminum. Racks are available in three different configurations: the 45° Rack Kit; the 30-60° Rack Kit, an adaptable rack capable of installations at both 30° 60°; and the Flush Mount Kit. All Rack Kits are available in versions for both Standard (Vertical) or Wide (Horizontal) collectors.
The Flush Mount Kit is used for installations where the roof structure itself is at the proper angle to mount the collectors. The 45° and 30-60° Rack Kits are designed for flat roof installations or for other installations where the existing roof angle is not optimal by itself.
The simple, strong u-channel design of our racks can withstand high wind and heavy snow. Stiebel Eltron mounting systems can be assembled using only two different socket sizes. Additional mounting components, such as hardware, in addition to flush mount and fixed angle racks, are available.
Flush Mount Racks come standard with SOLkits, but the raised rack kits can be specified with any SOLkit order when the need arises.
Solar Water Heaters Guide: 5 Key Aspects to Understand (2023 updated)
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Written by Christian Yonkers
Christian Yonkers is a writer, photographer, filmmaker, and outdoor junkie obsessed with the intersectionality between people and planet. He partners with brands and organizations with social and environmental impact at their core, assisting them in telling stories and spreading verifiable information that change the world for the better. Christian aims to have a sizable impact on the world helping foster a sustainable relationship between humans and the planet. Learn About This Person
Reviewed by Irma Omerhodzic
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Find the best price from solar installers in your area.
While the upfront cost of a solar water heater may be higher than traditional water heaters, the solar energy you’ll harness can yield great savings and environmental benefits. Heating water accounts for 18% of a home’s energy use, but doing so with solar energy could cut your water heating bills by 50 to 80%.
In this article, we’ll explain how a solar-powered hot water heater can help you tap into a free, renewable energy source, potentially saving money and doing good for the planet. With this information, you can make the best decision about whether a solar water heater is a good investment for your home’s hot water needs.
To see how much a full home solar system would cost for your home, you can get a free, no-obligation quote from a top solar company in your area by filling out the form below.
Solar Water Heater Basics
A solar hot water heater’s basic function is to expose water or a heat-exchanging liquid to the sun’s rays, then circulate the warmed liquid back into your home for domestic use. The basic components of one are a storage tank and a collector to trap the sun’s heat.
Collectors are a series of flat plates, tubes or tanks through which water or a heat transfer fluid passes and absorbs the sun’s heat. From there, the fluid is circulated to either a water tank or heat exchange unit.
While solar water heaters are most commonly used as energy-saving devices to preheat water before entering a conventional water heater in the home, some warm and store water without the use of a conventional tank, offering totally sun-powered hot water.
Types of Solar Water Heaters
Solar hot water heaters are split into two broad categories: passive and active. The primary difference between the two is that active systems require circulating pumps to move water, and passive systems rely on gravity to move water. Active systems also require electricity to operate and may use antifreeze as a heat exchanger fluid.
In the simplest of passive solar collectors, water is heated in tubes, then piped directly to a faucet when needed. Active solar collectors either use antifreeze — which is passed from the solar collector into a heat exchanger that heats potable water for storage and household use — or just heat water directly, which is then pumped to a water tank.
Active and passive systems have subcategories that are specialized for various climates, tasks, capacities and budgets. The one that’s right for you will depend on factors including:
Let’s take a look at each type of solar hot water system and how it can benefit your home.
Active Solar Water Heaters
Though more expensive than passive systems, active solar water heaters are more efficient. There are two types of active solar water heating systems:
In an active direct system, potable water passes directly through the heat collector and into a storage tank for use. They’re best suited for mild climates where temperatures rarely go below freezing.
Active indirect systems circulate a non-freezing fluid through the solar collector and into a heat exchanger, where the fluid’s heat is transferred to potable water. The water is then circulated into a storage tank for domestic use. Active indirect systems are a must for cold climates where temperatures regularly dip below freezing. Without an active indirect system, pipes run the risk of freezing and bursting.
Passive Solar Water Heaters
Passive solar water heaters are the less expensive, simpler option but also tend to be less efficient than active systems. They can, however, be more reliable and last longer, so you shouldn’t overlook them as an option, especially if you’re on a budget.
All passive systems use pressure or gravity to circulate water, and come in two variations:
Integral Collector Storage and Batch Heaters
Integral collector storage (ICS) systems are the simplest of all solar water heating units — the heat collector also serves as the water storage tank. They’re quite efficient but only work in climates with little risk of freezing temperatures. ICS systems can be as simple as a large black tank or a series of smaller copper tubes fastened to a roof. ICS units with copper tubing heat faster due to the increased surface area but lose heat faster for the same reason.
ICS systems are usually used to preheat water for conventional heaters. In such a system, when water is needed, it leaves the storage tank/collector and enters a conventional water heater in the home.
An important thing to consider with an ICS system is size and weight: Because the storage tank itself is also the collector, they’re large and heavy. A structure must be strong enough to support bulky ICS systems, which may be impractical or impossible for some homes. Another drawback to an ICS system is its tendency to freeze and even burst in colder weather, making them suitable only for warmer climates or otherwise drained before cold weather hits.
Thermosyphon Water Heaters
Thermosyphon systems rely on thermal circulation. Water circulates when warm water rises and cool water descends. They feature a tank like an ICS unit but have collectors attached sloping downward from the tank to allow thermal circulation.
Thermosyphon collectors gather sunlight, sending heated water back to the tank via a closed-loop or heat pipe. While thermosyphons are more efficient than ICS systems, they can’t be used where regular freeing occurs.
How Much Does a Solar Hot Water Heater Cost?
The more hot water you use, the more likely a solar water heater will pay for itself over time. Solar hot water heaters are most cost-effective for households with many members or a large hot water demand.
A typical solar water heater will cost around 9,000 before federal incentives, with higher capacity active models reaching upwards of 13,000. Small systems may cost as low as 1,500.
vary dramatically based on many factors, including the materials you choose, system size, installation and maintenance costs, and more. While ICS systems are the cheapest option (around 4,000 for 60-gallon units), they won’t work in all climates, so if your home sees regular temperatures below freezing, you’ll have no other choice than to fork over the cash for an active indirect system, or at least use a different system only part of the year.
Weight and size of cheaper passive systems might not be appropriate for everyone. If your structure won’t accommodate the weight of a passive system or you don’t have the room, a more expensive active system is yet again your best option.
If you’re building a new home or refinancing, you can roll the cost of a new solar hot water heater into your mortgage. Including the cost of a new one in a 30-year mortgage will cost you between 13 and 20 per month. Tack on federal incentives, and you might pay as little as 10 to 15 per month. So if you’re building new or refinancing, and your conventional water heating bills are over 10 to 15 per month, you’ll immediately start saving money. And the more water you use, the faster the system will pay for itself.
Aside from the cost to purchase and install the system itself, you’ll need to account for annual operating costs. In a simple passive system, this could be negligible or nothing. But in most systems utilizing conventional water heaters in tandem with a solar heater, you will bear some heating costs, albeit much lower than operating a conventional heater alone.
Tax Credits for Solar Water Heaters
You don’t have to shoulder the entire price of a new solar water heating system. Federal tax credits may significantly reduce the cost of installing one. Federal Residential Renewable Energy Tax Credits (also known as ITC, or Investment Tax Credits) can provide a 26 percent tax credit on solar water heaters. But there are some conditions to qualify:
- At least half of the energy generated from the property must come from the sun (photovoltaic systems).
- The new solar hot water heater must be certified by the Solar Rating and Certification Corporation (SRCC) or a similar entity endorsed by the government of the state in which the system is installed.
- The solar heating system can’t be used to heat swimming pools or hot tubs — it must heat water used within the home or business.
Many states, municipalities and utilities offer their own incentives and rebates for solar water heater installation. Check out the DSIRE database for more regulatory information.
Where to Get a Solar Water Heater
Solar hot water heater components are readily available in many national chain stores, such as Home Depot. Units are also available for purchase directly from producers, with Duda Diesel and Sunbank Solar offering several great residential options. Local installers may also offer quality units.
For solar pool heating and small-scale use, check out the heaters below:
- Duda Solar 30 Tube Water Heater Collector: This system is the perfect choice for heating pools, hot tubs and closed-loop systems. Thirty highly efficient unpressurized tubes provide excellent sunlight absorption and are rated at up to 45,000 BTUs a day.
- Sunbank Solar 40 Gallon Solar Water Heater: This is designed for households with one to three members. This thermosyphon system offers exceptional absorption efficiency (92-96%) and keeps hot water hot all day in an ultra-insulated built-in tank. Weighing in at just 180 pounds, it can be installed on most roofs.
- Duda Solar 200 Liter Water Heater Active Split System: This full kit comes with a stainless-steel water tank, controller and submersible water pump. It’s a dual-coil system, which allows you to heat the water in the tank both with solar power and a secondary electricity or heat source.
Because so many factors influence which solar water heater you should buy, it’s advisable to work with a professional when choosing and installing a larger solar water heating system.
Solar Hot Water Heaters Vs. Home Solar System
Solar water heaters are less common than they used to be. This is largely due to the drastic decline in the cost of solar panels, causing many people who would otherwise install solar water heaters to forgo them and heat their water with electricity generated from their own solar panels.
Solar water heaters take up precious real estate, and for a homeowner interested in producing their own solar-generated electricity, it may make more sense to maximize the space available and nix solar water heating altogether, buying solar panels instead.
However, if you don’t have the space for solar panels, solar water heaters may still be a great fit, as they take up far less room than solar panels do. Solar water heaters can also be a great option for those living in remote locations or as an environmentally friendly add-on for existing solar electricity generation. Modern electric water heaters are incredibly efficient and, when powered with solar electricity and paired with a solar water heater, will yield significant savings for your book and cut down your greenhouse gas emissions.
For many homeowners, the decision comes down to price. Solar hot water heaters can cost upwards of 13,000. To see how much a full home solar system would cost for your home, you can get a free, no-obligation quote from a top solar company in your area by filling out the form below.
FAQ: Solar Hot Water Heater
Is a solar water heater worth it?
Whether a solar water heater is worth it all depends on where you live, your needs and preferences, and whether you plan on installing solar panels. They have been losing ground due largely to the surge of home solar: The folks that would install them also want solar for electricity generation and often choose to eliminate solar water heaters that compete for valuable rooftop space.
If you have the space, a solar water heater will likely lower your water heating bills. Used in tandem with other renewable energies, it is still a great choice for nearly any application.
What is the price of a solar water heater?
A typical solar water heater system will cost around 9,000, with higher-end models reaching upwards of 13,000. Small-scale use heaters will be much cheaper, running between 1,000 and 3,000.
What are the disadvantages of solar hot water heaters?
The biggest disadvantage of a solar water heater is that it won’t work on foggy, rainy or cloudy days, nor at night. While this can be overcome with a conventional auxiliary heater, it is still a disadvantage all solar technologies share. Maintenance can be another turn-off. While generally requiring little maintenance, some need regular draining, cleaning and protection against corrosion.
How does a solar water heater work?
Solar water heaters circulate liquid through a solar collector — most commonly a flat-plate collector or tube collector — heating the liquid and sending it either to a tank for use or an exchanger, where the liquid is used to heat water for home use.
Christian Yonkers is a writer, photographer, filmmaker, and outdoor junkie obsessed with the intersectionality between people and planet. He partners with brands and organizations with social and environmental impact at their core, assisting them in telling stories that change the world.
Christian Yonkers is a writer, photographer, filmmaker, and outdoor junkie obsessed with the intersectionality between people and planet. He partners with brands and organizations with social and environmental impact at their core, assisting them in telling stories and spreading verifiable information that change the world for the better. Christian aims to have a sizable impact on the world helping foster a sustainable relationship between humans and the planet.
Irma joined the EcoWatch team in August 2015. She holds a Master’s degree and Bachelor’s degree from the E.W. Scripps School of Journalism at Ohio University in Athens, Ohio. She is a member of Kappa Tau Alpha – a national honor society of journalism.
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Why aren’t solar water heaters more popular in the U.S., even in solar-friendly states like California?
Despite widespread global success and huge opportunity for reducing fossil fuel demand, solar water heating is virtually unheard of in the U.S. Evidence suggests our demand for simple fixes is to blame.
Photo © iStockphoto.com | AlSimonov
Writer Dina Berenbaum Data scientist and environmental technology enthusiast
Writer Manoshi Datta @DattaManoshi Computational biologist and freelance writer
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October 28, 2020 — For Gershon Grossman and Ed Murray, 1978 was a big year. Grossman, then a solar energy pioneer at the Technion, Israel’s premier technological institute, was launching the first International Conference on the Application of Solar Energy. Murray, an idealist attending college, joined an upstart solar heating company in Sacramento, California’s capital, drawn by a prescient concern about climate change and, as he puts it, an impulse to “save the world.” For both, the excitement was palpable. Solar water heaters were surging into the market, solar thermal energy showed broad potential, and the two were riding the wave.
Four decades later, however, they live in two different worlds. In Israel, 85% of households get hot water from a dud shemesh, or “sun boiler.” But in the U.S., despite decades of advocacy by Murray and others, the number of households that have a solar water heater is less than 1%. I n California, many people don’t even know the technology exists.
America’s solar water heating deficit is often portrayed as a historical accident driven by the vagaries of politics and comparatively cheap fossil fuels. However, interviews with academic and commercial players on the front lines of the solar thermal industry, and a recent in-depth report on the now-expired California Solar Initiative–Thermal (CSI-T) program, suggest that the desire for simple, “magic bullet” solutions to climate change has also played a significant role in relegating this practical technology to the sidelines.
A Mandate, an Election and Two Roads Diverged
Heating water accounts for 25% of residential energy use worldwide, mostly achieved by burning fossil fuels. Solar water heaters do the job without combustion. Unlike solar photovoltaic (PV) systems, which convert sunlight into electricity, solar thermal systems collect solar energy as heat. Solar water heaters t ransfer this heat to water in a holding tank. Other energy sources, such as natural gas or electricity from a power grid, serve as a backup for cloudy days.
By tapping the sun, solar water heaters can reduce a household’s water heating fuel consumption 50% to 70%. And Israel is just one of dozens of countries with a variety of climates where this technology has been deployed. Solid performance and wide applicability have made the technology one of Project Drawdown’s top 50 climate change solutions.
So why did solar thermal technology soar in Israel and sputter in California, setting Grossman and Murray on such different life paths? A pair of political decisions in the 1970s and 1980s had dramatic impact.
The Yom Kippur War of 1973 and subsequent oil embargo made energy independence a matter of national security worldwide, but the pinch was particularly painful in countries lacking oil production. For Israel, the threat was existential; as former Israeli prime minister Golda Meir famously quipped, “[Moses] took us 40 years through the desert in order to bring us to the one spot in the Middle East that has no oil.” In 1976, Israel mandated solar water heaters for all new residential buildings up to eight stories tall — a mandate that was extended to all residential buildings in December 2019.
For Grossman, now a professor emeritus at the Technion and h ead of the Energy Forum at the Neaman Institute for National Policy Research. mandating solar water heaters made sense environmentally, even beyond Israel’s political agenda. “You just can’t argue with the numbers on how much [energy] you can save using solar water heating instead of electrical heating.”
The United States also felt the jolt of the oil embargo and feared running out of domestic oil. Supported by President Jimmy Carter’s 1978 federal tax credits for renewable energy. Americans installed nearly 1 million solar thermal systems by 1990, supplied by more than 200 U.S. manufacturers, including leading corporations such as Grumman Aerospace Corporation and Sears Roebuck.
In Israel, 85% of households get hot water from a dud shemesh, or “sun boiler.” In the U.S., it’s a different story. Photo courtesy of Yaniv Hassidof
However, in contrast to Israel, America’s commitment to renewable energy proved ephemeral. Under President Ronald Reagan, the federal incentives lapsed, dealing the solar thermal industry a body-blow. “We went from 650 companies in California that were installing solar [water heaters] to about 37 overnight,” recalls Murray. who is currently the president and CEO of two California companies dedicated to manufacturing, distributing and installing solar thermal systems, as well as president of the California Solar and Storage Association.
Recent attempts to revive the residential solar water heater industry have had limited success. The CSI-T program, begun in 2010 as a larger push to incentivize solar installations statewide. aimed to add 200,000 systems, but received only 6,237 applications for residential retrofits in 10 years, according to the program’s December 2019 report. “I could put a sign over the front door of my office that says ‘free solar water heating,’ and they’d probably still stay away in droves,” Murray says with a wry laugh.
Larger installations for apartment complexes, hotels and universities, and home pool heating have helped keep Murray’s solar thermal business es afloat despite the lack of other residential demand. Ironically, the commercial sector isn’t as robust in Israel because the country’s original mandate only applied to residential properties — a move Grossman views as a significant oversight. Indeed, Grossman believes that an industrial mandate could increase Israel’s renewables usage up to fivefold.
The Limiting Psychology of Renewables
The woes of the American solar water heater industry go far beyond politics, however. The industry also suffers a more insidious challenge: For the average consumer, “going solar” means just one thing: solar PV.
Solar thermal technologies, including solar water heating, provide a direct, thermodynamically efficient and cost-effective method for decarbonizing heating. And for households in mild climates with low electricity bills, “solar water heating can be one of the simplest ways … to use renewable energy and save on energy bills,” says the CSI-T report.
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But it’s solar PV that has exploded into the global electricity sector, thanks to manufacturing innovations and strong government support. Leveraging economies of scale, the price of solar PV panels has dropped by over an order of magnitude in the past decade. In California, additional boosts came from government-instituted solar feed-in tariffs, cheap financing plans and private-sector investments. And, in a major coup for the industry, California mandated solar PV on new residences up to three stories starting 2020.
On the other hand, California’s residential solar water heater industry finds itself in a vicious cycle of low consumer demand and high prices. As the CSI-T report notes, “In contrast to conventional gas and electric water heaters, which are typically installed by plumbers, solar water heaters are installed by a range of firms and public entities.” In other words, consumers must actively seek out solar water heaters by relying on nonstandard sales channels.
This additional friction reduce s consumer demand among all but the most motivated consumers. leading to higher marketing costs that drive up the customer’s bottom line. in California are further exacerbated by past industry failures, which have led to strong, self-imposed regulations in the name of consumer satisfaction, says Murray. For example, after many cheaper solar water heating systems froze during the unprecedented 1990 freeze in California, only more expensive systems were allowed through the CSI-T program.
All told, the cost of the average solar water heater sold in California through the CSI-T program was US7,400, compared to less than US1,000 for a fossil fuel alternative. By contrast, a solar water heater in Israel can cost as little as US700.
Rather than embracing the growing portfolio of technologies available to solve the carbon emissions problem, going all-in on one satisfies the very human need for “magic bullets.”
Today, drumming up excitement for solar thermal remains difficult. According to CSI-T report interviews with solar water heater adopters, “Some interviewees remarked that it seemed tough to get others interested, theorizing that PV was so dominant in neighbors’ minds that solar water heating hardly registered.”
“It’s just the sizzling, sexy PV [that] really captivates the audience,” says Murray.
Portfolios, Not Magic Bullets
Entrepreneurs routinely caution, “Fall in love with the problem, not the solution.” In this case, the problem is carbon emissions, and, against entrepreneurial advice, individual governments have tended to fall in love with just one solution. For Israel, Cyprus, Hawaii and others, solar water heaters were that solution. For California, it’s solar PV.
By committing to a specific technology, governments fall prey to a conceptual error that science journalist Ed Yong recently referred to as a “ monogamy of solutions . ” (Interestingly, he argues this fallacy also shapes the government’s response to Covid-19.) Rather than embracing the growing portfolio of technologies available to solve the carbon emissions problem, going all-in on one satisfies the very human need for “magic bullets.”
Europe’s Green Deal may model such a “portfolio” approach for the rest of the world, according to Bärbel Epp, a German physicist-turned-journalist with nearly two decades of experience studying the global solar thermal market. According to Epp, representatives from the European solar thermal market have lobbied the European Commission for over a decade to use solar thermal technologies to decarbonize the heating sector. “It took [the solar thermal industry] I don’t know how many years, at least 10, of just continuously repeating the sentence that heat is 50% of our final energy consumption in Europe. … It was hard to lobby in Europe, but it’s now obvious that we have to do something for heat.” Whether these efforts will succeed in providing solar thermal a seat at the table remains to be seen.
To Grossman, solar water heaters are the first piece of Israel’s portfolio. As Israel struggles to meet its Paris Agreement goals, Grossman says he believes solar PV panels will take their place alongside solar water heaters on Israel’s rooftops.
Back in Sacramento, Murray is still battling for solar thermal. This year, he’s lobbied the California legislature to extend the state’s recently expired solar thermal subsidy program for one more year, citing Covid-19 as a barrier. The legislature hasn’t budged, but Murray vows he’ll keep going. He may be a lot older than he was in 1978, but the idealism is still alive.
Editor’s note: Dina Berenbaum and Manoshi Datta wrote this story as participants in the Ensia Mentor Program. The mentor for the project was Peter Fairley.
Editor’s note, 11/3/20: This story was updated to give more information about Gershon Grossman’s current role.
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