Did you know that Maine has 450,000 homes heated with oil? This dependence on a foreign fuel source makes us vulnerable to supply disruptions and price volatility—not to mention the fact that we are polluting the northeast with the highest per capita CO2 emissions of all New England states.

Using sunshine to produce hot water for showering, laundering and dish-washing is a practical way to make a positive impact on the environment while saving money at the same time. After 10 years of designing and installing hundreds of solar hot water systems in Maine’s challenging climate, we’ve distilled our knowledge and experience into a robust design that offers the highest efficiency and durability. Maine Solar Energy can tailor its time-tested, field-proven system design to integrate with most existing water heating systems, whether it is gas, electric or oil-fired.

Solar hot water is the most common system type in Maine because it provides the quickest return on investment. This is because solar hot water substantially reduces fossil fuel consumption and CO2 emissions, particularly when an oil boiler or electricity is being used to produce domestic hot water. A properly designed solar domestic hot water system can save more than 300 gallons of oil per year and reduce greenhouse gas emissions by more than 5,000 lbs., depending on your existing situation.

How it Works
Solar hot water collectors are typically mounted on a south-facing roof or wall, 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, solar pump and electronic controls.

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. Sun-heated antifreeze is pumped down from the collectors and circulated through a heat exchange coil located in the bottom of the storage tank, thereby transferring the heat from the sun to your domestic hot water supply. We design automatic hot water 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. The solar storage tank has a secondary heat exchange coil located in the top of the tank, which is plumbed to your existing heating system for backup. If this is not possible, alternative solutions include using a special tank with an electric element for backup or installing an on-demand hot water heater.

Basic System Schematic

Solar Hot Water Collectors: Evacuated Tubes & Flat Plates
After years of researching and experimenting with different brands of collectors, we have come to the conclusion that Apricus evacuated tube collectors offer the best performance at the most reasonable price. Apricus is a global leader in evacuated tube technology based in Australia. We generally recommend evacuated tube technology over flat plate collectors because the tubes’ vacuum insulation design prevents system heat losses in Maine’s relatively cold climate. Plus, the cylindrical shape of the tubes enables them to better harvest low-angle wintertime sun at our northern latitude.

Evacuated Tube Array

Flat Plate Solar Hot Water Collectors
For applications where high demand will come in the warmer months (seasonal homes, i.e.), or where cost is a primary concern, we offer Stiebel Eltron flat plate collectors and Chromagen Collectors. The Stiebel Eltron collectors have been manufactured in Germany by a family-owned business for more than 50 years and we have had excellent results over the years with this product.

Stiebel Eltron Flat Plates

Solar Storage Tanks
We wanted to know how much heat is lost in our solar storage tanks overnight, so we ran our own test and found that the super-insulated Stiebel Eltron tank loses less than .5 degrees F per hour. This means that if you heat your tank up to 150 degrees during the day, it will lose just 6 degrees from 6 p.m. to 6 a.m. We believe Stiebel Eltron manufactures the best dual coil solar storage tank on the market. Stiebel’s purpose-built tanks have 3 inches of foam insulation 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 enamel-lined steel tank comes with a sacrificial anode that is easy to view and replace if necessary.

Estimated System Costs Before State & Federal Incentives
30-tube collector with 80 gallon storage tank for 1-2 people:   $9,500 to $10,500
40-tube collector with 80 gallon storage tank for 2-3 people:   $10,000 to $11,000
50-tube collector with 105 gallon storage tank for 3-4 people: $10,500 to $11,500
60-tbue collector with 105 gallon storage tank for 5-7 people: $11,500 to $13,000
Flat Plate systems are generally 8% less

*Cost variables are number of collectors, tank size, difficulty of roof installation, difficulty of pipe installation, difficulty of tank installation and project distance from Portland, Portsmouth, Bangor or Liberty.

Government Financial Incentives
The federal tax credit is 30% of total system cost.

Solar Domestic Hot Water Rules of Thumb:
Each 20-tube collector array will generate roughly 15,000 BTUs of clean heat energy per day
Each 30-tube collector array will generate roughly 22,500 BTUs of clean heat energy per day
1 Stiebel Eltron SOL 25 collector will generate roughly 21,000 BTUs of heat energy per day
1 gallon of home heating oil contains 139,000 BTUs of energy, but most oil boilers burn at roughly 75% efficiency in winter and 15% efficiency in summer to produce domestic hot water
1 gallon of propane contains 91,000 BTUs of heat energy

Solar Space Heating
If you have a super insulated home (R30 walls, R50 ceilings) and radiant heat distribution, there is a chance that solar space heating could work for you. Because it is a challenging application, we recommend that you contact us to determine if solar space heating is viable for your specific situation.

Basic Questions to Assess Solar Hot Water Viability For Your Home

  • Do you have a south-facing roof section that is shade-free from 9 a.m. to 3 p.m. year round?
  • Do you have a patch of nearby ground that is shade-free from 9 to 3?
  • Is there a practical pipe run from the collectors to your basement?
  • Is there space for a solar storage tank in your basement and can something 29” wide fit through a door or bulkhead?

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Maine Solar Energy Company
142 Presumpscot Street   Portland, Maine 04103
Phone: (207) 232-6595   E-Mail:

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