Why

Solar water-heating systems can provide up to 70% of a household’s annual hot-water needs. Since half of the gas used in a typical home in this region is used to heat water, this can amount to considerable utility bill savings. Heating water with the sun also provides a cushion from future fuel shortages and price increases since it makes use of a free, unlimited energy source.

“If someone is really interested in renewable energy, and they want to get involved somewhere, the best place to start is with a domestic hot-water system. These systems are still the most cost-effective solar technology on the market today.”says Peter Codella of Codella Solar and Associates.

Recommendation

Consider installing a solar water-heating system. If the cost of installing a system is prohibitive today, consider pre-plumbing for a future solar installation. The more water you need to heat, whether in residential or commercial applications, the more money a solar water-heating system can save. These systems are most often used on single-family homes, though they are appropriate for commercial applications which have considerable hot water needs. The majority of installed systems are used to heat swimming pools.

Solar Water-Heating Basics

A typical solar water-heating, or “domestic hot water,” system is made up of collectors, a storage tank, and, in some systems, an electric circulating pump and a temperature control.

The solar collector, usually a thin black plate, is mounted on a building’s roof and resembles a skylight. Water runs through small tubes under this plate and is heated by the sun. The hot water then flows into a well-insulated storage tank. In household systems, a solar water heater storage tank usually connects to the existing water heater, which only turns on when needed.

Passive and active systems: Passive systems circulate water from the solar collector to the storage tank using warm water’s natural tendency to rise. Some passive systems (so-called “batch” systems) eliminate the tank completely; the heater water (40-60 gallons) is stored within the collector itself. Active systems use small electric pumps to increase the efficiency of the water circulation. Because active systems use electricity, they will not function in a power outage (unless powered by solar-electric panels with battery backup). Passive systems may be somewhat less efficient, but they are essentially maintenance free over their lifetime.

Swimming pool systems: Solar swimming-pool-heating systems do not heat the water to the same high temperatures required of household systems. The pool’s existing filter pump is used to move water to the solar collector to be heated, and then back into the pool. These collectors differ from domestic solar water-heating systems as the collectors have no glass and are not insulated. Solar heating systems can provide 50 to 100 percent of the energy needed to heat a pool.

Design Details

Sizing Your System: Sizing a solar water heater involves determining the total collector area and the storage volume required to provide 100 percent of your household’s hot water during the summer. Solar-equipment experts use formulas to determine what size system is needed.

The amount of hot water a solar water heater produces depends on the type and size of the system, the amount of sun available at the site, the temperature of the water flowing into the system, proper installation, and the tilt angle and orientation of the collectors.

Positioning your system: Solar water heaters will work best with a south-facing location; the next most favorable location is west-facing. East-facing and flat roofs can also work in some situations. Your local solar equipment dealer can perform a solar site analysis for you or show you how to do one on your own.

Rooftop installations are the most common, but the collectors can also be mounted on accessory buildings, or on ground mounts. A rooftop system must be sensitive to the integrity of the roof. The local building department may require verification that the existing roof can support the added weight of the solar collectors.

Tankless Water Heaters: With use of an insulated water storage tank, solar water heaters can work quite well with tankless water heaters. Just make sure the water heater is thermostatically controlled; these units are designed to register incoming water temperature and apply heat as needed to reach the desired output water temperature. Most modern tankless water heaters now have this feature.

Too many shoddy solar water-heating systems were installed by poorly trained contractors in the ’70s, giving these systems a bad reputation. Make sure your installer is experienced. Look into the warranty: If the dealer you are buying from goes out of business, can you get still get support and parts from the manufacturer or a local plumbing contractor?

Cost and Cost Effectiveness

The more water you need to heat, the more money a solar water-heating system can save. The cost of an installed household system runs about $4,000-$6,500, for a one-story home system; more for two-stories. The cost of an installed pool system runs about $4,500-$5,500. A building permit is required, and this may add an additional $500-$600 to the cost for an engineering report that certifies that the roof is strong enough to support the additional weight (this report generally would not be required for pool systems).

The price of copper has increased significantly recently, causing the cost of solar water-heating systems (and many other plumbing systems) to dramatically increase.

Federal tax credits of 30% of the system costs, up to $2,000, are available for certain systems. For a system to qualify, it must be certified by the Solar Rating & Certification Corporation or the Florida Solar Energy Center. Pool systems do not qualify for the tax credit.
The directory of qualifying equipment can be found here: www.solar-rating.org/ratings/ratings.htm

A well-designed and properly installed system can show paybacks of 8 to10 years (depending on hot-water use and costs of natural gas). A solar pool heating system has a typical payback period of between 2 to 4 years. A four-year payback, looked at another way, is a 25% return on investment. It isn’t very often you can double your money in four years.The payback on pool systems is generally much quicker than on a household system because they heat so much more water.

After the payback period, you accrue savings over the life of the system, which ranges from 20 to 40 years, depending on the system and how well it is maintained. Solar energy costs never increase.

The National Remodelers Association reports that adding a solar water heater to an existing home raises the resale value of the home by the entire cost of the system.

If you are building a new home or refinancing a present home to do a major renovation, the economics are even more attractive. The cost of including the price of a solar water heater in a new 30-year mortgage is usually between $13 and $20 per month. In most cases you’ll be saving much more than that on your monthly gas bill, so you are ahead right away. How much is that granite countertop going to save you on your monthly utility bill?

To pre-plumb for a future solar water-heating system, plan to spend about $600.