Solar Hot Water Heaters (Solar Thermal)
Evacuated tube solar hot water collectors installed on a home in Southwest Harbor, Maine
Save Money With Free Hot Water from the Sun
Most homes in Maine, New Hampshire, and Massachusetts heat their water using high-mass oil boilers. All summer these boilers must stay on, sporadically firing to heat domestic hot water.
Solar hot water counters this situation by providing solar-heated water during the summer months, allowing you to:
- Shut down your home's boiler from May through October
- Save 100s of gallons of oil
- Have reliable hot water throughout your home
Not only do homes with solar hot water save money and C02 emissions, most customers report that showers with solar hot water just feel better!
Professional System Design and Installation
After 10 years installing and servicing solar hot water systems in the harsh climates of Maine and New Hampshire, we've distilled our knowledge into a design we believe to have the highest efficiency and longevity, with the lowest installation costs.
ReVision Energy's solar thermal systems are compatible with any existing water heating system, whether it's electric, gas, or oil-fired. During our free solar site evaluation one of our highly trained, experienced solar designers will visit your home and evaluate whether a solar energy investment makes sense for you.
Our systems featured a 'closed-loop' design, meaning that we use nontoxic antifreeze that never comes in contact with your drinking water to exchange heat. Our systems operate trouble-free throughout the winter, and are designed for automatic overheat protection so that you can leave the system unattended in summer without issues.
How Solar Hot Water Works
Solar hot water has several major components:
- Collectors on the roof (collect heat)
- Storage tank in basement (stores heat)
- Pipe run from basement to roof (moves heat down from roof)
- Pump station/sensors on tank (turns on pump when there is heat available on roof)
Whenever sunshine makes the solar hot water collectors hotter than the water in the bottom of the solar storage tank, an electronic sensor automatically turns on the solar pump affixed to the tank.
Non-toxic antifreeze is pumped from the basement to the collectors; after being heated by the sun it is pumped back down to the basement and circulated through a heat exchange coil located in the bottom of the solar storage tank, thereby transferring the heat from the sun to your domestic hot water supply. When you run a shower, or wash your hands, the hot water from the solar storage tank flows up and into the tap in your house.
ReVision Energy builds automatic backup into all solar domestic hot water systems so that when the sun can't get the job done, you don't have to worry about cold showers. We can tie into an existing oil boiler with a dual-coil tank, preheat another water tank, or install a solar tank with an electric element for backup.
See It Explained in an Animation:
Solar hot water collectors are typically mounted on a south-facing roof section, but we also have plenty of experience ground-mounting systems when the roof is not a viable option. Major system components include the collectors, a purpose-built solar storage tank, copper piping, circulating pump and electronic controls.
Am I a Good Candidate for Solar Hot Water?
Solar hot water makes the most sense for:
- Homes inefficiently heating water now (i.e. using an oil boiler or old electric tank)
- Primary homes or homes used year-round
- Homes with high hot water loads (families of 4+, apartments)
Use our interactive solar hot water calculator to see what kind of system might work for your home:
What Goes In a Solar Hot Water Job?
ReVision Energy borrows from leading European solar thermal system designs for robust, resilient systems designed to sustain decades of New England winters. Our solar hot water systems are a closed loop design, meaning that the fluid that passes through the solar hot water collectors never comes in contact with your drinking water supply (and thus can be winterized), and feature the industry-accepted best practice of steamback design for overheating.
There is much more in a solar hot water quote from ReVision Energy than the quotes by most other dealers. Here is a brief summary of the major components and how/why we select them.
Solar Hot Water Collectors
There are two major designs of solar hot water collectors - evacuated tube collectors and flat plate collectors. We are unbiased in our choice of collectors and choose the collector best matched for the application. Both designs are productive and efficient, but they offer unique characteristics that determine in which situations they are best suited.
Evacuated tube solar collectors tend to offer the best year-round performance, as they feature incredible vacuum insulation that prevents system heat losses in Maine's relatively cold climate. The cylindrical shape of the tubes enables them to better harvest low-angle wintertime sun at our northern latitude. They do not shed snow as well as flat plate collectors, but overall they are better winter performers which makes them a preferred choice for most residential installations.
Historically, flat plate solar hot water collectors have offered superior summer performance, making them a better choice for homes with higher summertime hot water loads. However, this is changing with our adoption of the incredible Wagner Euro C-20 flat plate collector. Wagner is known as a solar pioneer in Germany and started designing, producing, and improving collector design 32 years ago. The Wagner C20 collector is the most efficient flat plate collector that is available in the United States according to SRCC ratings.
Factors such as roof pitch, roof layout, expected hot water load (and seasonal demand), expected snow load, aesthetics and cost are all factors in determining whether evacuated tubes or flat plate solar hot water collectors are better for you.
The Solar Storage Tank
Stiebel Eltron 105 Gallon Solar Hot Water Storage Tank with Solar Circulating Pump
A purpose-built storage tank is critical to the success of a solar hot water system. It's critical that a solar storage tank be:
- Built out of rugged materials to perform well for the span of the system's life (20+ years)
- Well-insulated, with 2-3 inches of foam insulation to ensure minimal heat loss overnight from solar heated-water
- Properly sized for your household's needs; it should neither be too small, so that it stressed to keep up with demand, or too large, so that solar is never effective at provided a significant fraction of the home's domestic hot water needs
For installations with an oil boiler as backup, we choose Stiebel Eltron tanks as they manufacture the best dual coil solar storage tank on the market. Stiebel's purpose-built tanks are super-insulated with 3 inches of urethane foam to store precious BTUs harvested from the sun and its two internal heat exchange coils allow for easy integration with almost any boiler-based heating system. This porcelain-lined steel tank comes with a built-in sacrificial anode rod with a wear indicator that is easy to view and replace if necessary.
For systems requiring electric backup, we typically will install an 80 or 119 gallon Caleffi solar tank, and 2" of non-CFC rigid foam insulation which offer R16 insulating value.
Pump Controls
The "brains" of the solar hot water system is the pump station. Ours feature a high-quality 3-speed circulator, check valve/ball valve, pressure relief valve, fill and drain ports, flow meter and sight glass, temperature gauge and pressure gauge. System operation is governed by a variable speed differential temperature solar controller that is able to harvest more solar energy than DC-based systems, such as during low light or overcast conditions.
Oil Boiler Control Upgrades Typically Paired with Solar Hot Water
Solar hot water by itself will immediately save you money and heating oil. However, we've found that by adding several upgrades to your oil boiler you can reduce oil use even more.
Cold Start Boiler Control Option
Does your furnace kick on in the middle of a hot sunny summer day? This is a common problem in the northeast because most boilers are set up in a 'hot start' mode whereby the boiler maintains an internal temperature of 180 degrees 24/7, 365 days per year. This is terribly wasteful in the summer months and the shoulder seasons because roughly 85% of your heat energy is going up the chimney and warming your basement.
By converting a boiler to a 'cold start' mode in conjunction with a solar hot water system, we can effectively shut down the boiler from May to October. In this mode, the boiler only fires when it is called by a thermostat to produce heat, or called by the solar storage tank to provide supplemental hot water. This control upgrade is possible for most boilers and is generally included in our system quote.
Intellicon Boiler Control Option
Another control upgrade that can result in a savings of fuel is the Intellicon smart burner control. IntelliCon®-HW+ is a microprocessor-controlled, fuel-saving device for hot water (hydronic) heating systems. IntelliCon-HW reduces fuel consumption, wear on parts, flue emissions and electrical usage, when installed on any new or existing gas or oil burner. IntelliCon-HW+ saves energy by adjusting the burner run pattern to match the system’s "heat load."
Its action is similar to the industry-accepted method of "outdoor-air temperature reset control," but does not require an outdoor-air temperature sensor or the need to profile the building in order to adjust the "reset" controller properly. IntelliCon-HW+ determines the "heat load" by using an easily installed strap-on temperature sensor that monitors the boiler’s out-flow water temperature and the rate that this temperature is changing. The additional cost is assessed on a case-by-case basis.
Outdoor Reset Boiler Control Option
Outdoor reset controller modulates the boiler supply temperature based on outdoor air temperature. This enables the boiler to operate at an increased efficiency and reduce fuel consumption by roughly 10%. For addition information, log on to: www.taco-hvac.com/uploads/FileLibrary/OM01.pdf. The additional cost is assessed on a case-by-case basis.
Post Purge Upgrade Option
The solid-state Taco Post Purge Plug-In Card maintains power to the circulator once the priority zone is satisfied, but does not fire the boiler. The circulator purges excess heat into the priority zone, minimizing stand-by heat losses during warm weather months and optimizing boiler operation when used with a boiler reset control. Power can be maintained to the circulator from 20 seconds to 7 minutes using an adjustable potentiometer. The additional cost is assessed on a case-by-case basis.
Solar Space Heating
We're often asked whether we can integrate our solar hot water systems with conventional boilers to produce energy for space heating. Solar space heating is doable, but has a few special requirements:
- Solar space heating only makes sense in higher performing homes
- Solar space heating requires low temperature distributed (e.g. radiant floor) heating
- Solar space heating requires excellent southern exposure
For retrofits, solar hot water space heating is rarely a viable option. Solar is not great at heating water to high temperatures for baseboard heat, and even homes with existing radiant heat are usually not insulated enough to make the investment in a solar space heating system worthwhile - see our solar space heating page for more information about these systems and considerations.
If your home meets these basic requirements for solar, please contact us - we would be happy to continue the conversation.
Commercial Projects
Businesses that have high hot water usage can dramatically reduce their fossil fuel costs and CO2 emissions by having Revision Energy install a solar hot water system. See our commercial solar hot water page for more information about solar hot water for business.
Questions to Ask When Comparing Solar Hot Water Proposals
Not all solar proposals are created equal. Here are some questions any reputable solar hot water installer should be able to answer:
- Is this system designed specifically for my hot water demand or is this a generic system recommended by a component supplier?
- How did you determine the appropriate size for my system?
- If the system is sized to tackle 90-100% of the summertime hot water load (as it should be), what happens when I go on vacation in August and don't use any hot water for a week?
- Learn More:
How to Compare Solar Hot Water Proposals
