Solar thermal customer Andy Chase discusses his solar evacuated tube array, which has reduced his home’s oil use by roughly 300 gallons per year!

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 solves this problem 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 or propane
  • Have reliable hot water throughout your home

Not only do homes with solar hot water save money and reduce carbon pollution, most customers report that showers with solar hot water just feel better!

Professional System Design and Installation

Arrowsic, Maine - Solar Hot Water and Solar Power

Solar hot water panels (lower right) paired with a grid-tied solar electric array for a customer in Arrowsic, Maine.

After 12+ years installing and servicing solar hot water systems in the harsh climates of Maine and New Hampshire, we’ve distilled our knowledge into a set of design principles that we believe has the highest efficiency and longevity, with the lowest installation costs.

Our designs are proven in the field with over 1,000 happy customers in Northern New England, ranging from small single collector systems for retired couples, to dozens of collectors that produce hot water supplies for gymnasiums and restaurants.

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 solar hot water (or an alternative high-efficiency system like an electric tank or heat pump water heater) is a good fit for your family.

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.

0-down, 2.99% financing is available through ReVision’s Own Your Power solar loan program.

How Solar Hot Water Works

Solar hot water system operation:

  1. Sun hits collectors on the roof, heating non-toxic antifreeze mix and triggering pump to activate.
  2. Pump moves solar-heated mix from roof down into heat exchanger located in storage tank in basement, indirectly heating water supply.  This circuit continues as long as there is heat to be harvested on the rooftop.
  3. Hot water from storage tank pumps out to sinks, showers, dishwashers, etc.
  4. Backup automatically integrated to provide hot water during extended periods of cloudy weather.

Am I a Good Candidate for Solar Hot Water?

Solar hot water is far and away the most efficient water heating solution overall, but it especially makes sense for:

  • Homes inefficiently heating water now (especially those on oil  boilers; the more it costs you to heat water now, the quicker an ROI with solar).
  • Primary homes or homes used year-round (as seasonal or second homes will tend to not use enough water to make it worth the investment).
  • Homes with moderate to high hot water loads (families of 4 or more, as the fuel costs of any water heating solution add up).

What Components Drive a Solar Hot Water System?

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.

Not all solar thermal designs are created equal.  Our solution is not the least expensive, but with over a decade of experience, hundreds of satisfied clients, and rigorous field-testing, we are very confident that our solar hot water designs feature the very best value in terms of reliability and efficiency over the long term.  Here is a brief summary of the major components included in a solar thermal project and how/why we select them.

Solar Hot Water Collectors

Solar Hot Water Example

Two flat plate solar hot water collectors will provide upwards of 80% of a home’s domestic hot water needs on an annual basis

There are two major designs of solar hot water collectors – evacuated tube collectors and flat plate collectors. These days we tend to prefer flat plate collectors over evacuated tubes due to superior year-round performance, quality of workmanship, and reduced long-term maintenance vs. tubes.  Currently our collector of choice is the German-made Stiebel Eltron SOL27 collector, which offers an incredible 10-year warranty.  We have used Stiebel Eltron components for years and find their build quality and customer service to be second to none.

Complicating factors such as roof pitch, roof layout, expected hot water load (and seasonal demand), expected snow load, aesthetics and cost will influence our decisions, hence the reason that custom design by a seasoned solar professional is required on every job.

All solar hot water collectors operate on the same principle: heat from the sun passes through tempered glass and is captured by heat transfer fluid encased in copper.  There is insulation around the collectors to keep as much of that solar energy in; with evacuated tubes this is done with a vacuum seal (hence the name) while in flat plate collectors there is generally insulated at the sides and bottom of the frame.  Flat plate collectors feature various designs of copper tubing inside them such that flow rate and solar gain are optimized.

The Solar Storage Tank

Clean Green Energy Solar Power Hot Water Tank with Heat Exchanger

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. A solar storage tank must 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 has difficulty keeping up with demand), or too large (so that solar is never effective at providing 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, comprised of 2″ of non-CFC rigid foam insulation which offers 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. Our smarter RESOL controllers will harvest more thermal energy than a solar-panel + pump system during low-light situations such as early in the morning and in overcast conditions.

Heat Pump Water Heaters and Electric Tanks

Accelera heat pump water heaters

Stiebel Eltron’s Accelera heat pump water heaters are rated as most efficient in the USA

While some in the industry claim “Solar Thermal is Dead” we think those claims are greatly exaggerated.  However, there are indeed situations where solar PV is the best use of the solar resource at a home, and water heating needs are more effectively served by electric alternatives (powered by the PV, of course!).

Such options include heat pump water heaters and high-efficiency electric tanks.  Again, ReVision distinguishes ourselves as mechanical contractors by offering only the best equipment, such as Stiebel Eltron Accelera series heat pump water heater, which is the most efficient water heater in the US market.  Heat pump water heaters use a refrigerant process (similar to air source heat pumps) to extract heat out of conditioned indoor space and use it to heat domestic hot water.

Our choice of electric hot water tank is by Vaughn, a domestic manufacturer (based in Massachusetts) that produces a cement-lined water heater that is good for the life of a home.  The stone lining prevents any corrosion of the steel tank, which means that the tanks do not require anode rods.

There are numerous ways to produce hot water a home, the ‘best’ way will be custom-tailored to current and future needs, available resources and budget.  This is where we step in as energy professionals unbiased to a particular technology. Contact us for a free evaluation of the water heating options available to you.