Solar Hot Water (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 and New Hampshire heat their water using high-mass oil boilers. While this is fine in the winter, when the oil boiler is already running for heat, in the summertime the boiler must stay on even on the hottest days, running extremely inefficiently for domestic hot water.
With a properly sized solar hot water system, that same household will save more than 300 gallons of oil per year.
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!
Example Solar Electric Systems:
Click on any photo below for a larger version from our residential solar photo gallery.
Professional System Design and Installation
A home with flat-plate solar hot water collectors installed on a home in Merrimack, New Hampshire.
ReVision Energy's solar hot water 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.
How Solar Hot Water Works
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 non-toxic antifreeze is pumped 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.
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.
How Solar Hot Water Works
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.
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.
Solar Hot Water Resources:
Solar Hot Water Case Study- Solar Hot Water Mounting Options
- See sample systems in our residential photo gallery.
- Investing in A Solar Hot Water System - A resource by the Renewable Energy Resource Center of Vermont explaining benefits and payback of solar hot water.
Solar Hot Water Collectors
An AP-30 evacuated tube solar hot water system installed on a home in Freedom, Maine
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 a collector best match 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 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.
Flat plate solar hot water collectors tend to offer superior summer performance, making them a better choice for homes with higher summertime hot water loads. They are also nominally less expensive than evacuted tube collectors.
Want to learn more? View a video comparing flat plate and evacuated tube collectors by Fortunat Mueller, one of ReVision's resident engineers.
Solar Storage Tanks
Stiebel Eltron manufactures 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.
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 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.
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 4 p.m.?
- Do you have a patch of nearby ground that is shade-free from 9 a.m. to 4 p.m.?
- 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?
If your home meets these basic requirements for solar, please contact us - we would be happy to continue the conversation.
Why Go Solar?
SAVE MONEY
Because domestic hot water is something we use year-round, its production is the number two energy hog in most households, behind only space heating. From the very first day a solar hot water system is installed, you will save money that was previously spent on fossil fuel energy.
SAVE THE ENVIRONMENT
Each 30 tube solar collector saves 1,770 lbs of CO2, 4 lbs of sulfur emissions, and 5.4 lbs of nitric emissions each year (compared to electricity).
SOLAR SHOWERS FEEL BETTER
You'll feel better knowing you are doing your part to preserve our planet and save our environment. We can't promise you'll be cleaner, but you might end up taking longer showers knowing the heat is from the sun.
Getting Even More Out of Your Solar Hot Water Investment
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.
Oil Boiler Control Upgrades
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. We can help you solve these problems.
Cold Start Boiler Control Option
At ReVision Energy, we have found that modifying the controls on your boiler, in conjunction with a solar hot water installation, can save a bunch of oil and the associated CO2 emissions. By converting a boiler to a ‘cold start’ mode, we can effectively shut down the boiler for most of the time 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.
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
- 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
