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Active vs. Passive Solar Water Heating Systems


The average Houston household spends approximately $500 per year to heat their water. This expense, which is typically the second largest energy usage after heating and air conditioning, can be up to 18 percent of a monthly utility bill. An experienced Houston plumber can install a solar water heating system as an environmentally friendly, energy-efficient option to a traditional water heating system.

Solar power can also be a cost-effective alternative for households that use a large amount of hot water. The sun’s rays are a free source of renewable energy that can be used in many different climates. Solar water heating systems include a storage tank to hold the hot water and solar collectors designed to absorb energy from the sun. The water heater can be an active or a passive system. The most appropriate solar water heating system for your home is based on several factors.

Active Solar Water Heater

An active system uses a pump and controls to circulate water between the collectors and water tank. The system may use a direct or indirect method to circulate the water. The direct method circulates the water through the collectors and then back into the storage tank. This technique is best suited for Houston’s mild climate where temperatures seldom drop below freezing.

In the indirect method, a non-freezing heating fluid is circulated through the system. Energy is transferred from this fluid by a heat exchanger to heat the water contained in the storage tank. The indirect method is utilized more often in regions where low temperatures may cause pipes in a direct circulation system to freeze.

While these systems are more expensive to install, they are more energy efficient than a passive system. Houston plumbing company customers generally experience lower monthly utility bills that offset the additional expense.

Passive Heating System

A passive solar water heater uses the properties of natural convection to circulate water. As a result, the system requires fewer natural resources to build, maintain and operate. While not as efficient as an active system, passive solar water heaters are usually more reliable and last longer because they have fewer mechanical parts that must be serviced and maintained. Passive systems will continue to operate during a power outage and are usually less expensive for technicians to install. An integral collector-storage system is recommended for areas where temperatures rarely drop below freezing and for households with high daytime and evening hot water needs.

Thermosyphon passive systems are more expensive for a Houston plumbing company to install than their integral collector-storage system counterparts. In this highly reliable system, the collector is installed below the storage tank, which enables the warm water to rise from the collector and into the tank naturally without the assistance of a pump.

Cost versus Benefits

Solar hot water provides a green alternative to the traditional methods of heating water. Whether your Houston residential plumber installs an active or passive solar water heating system, your return on investment depends on several factors. These include your water usage, building orientation, the amount of available sunlight, and the optimum location for the solar collectors. Another important consideration is whether a backup conventional hot water system is required. The payback period will vary based on these and other factors, such as tax credits and changes in energy prices. An experienced professional can help you evaluate these factors.

Installation and Maintenance

The installation of a solar hot water heating system is critical to its overall performance. As a result, homeowners should entrust the installation to a qualified Houston plumber. Properly maintaining the system is also important. Consult with the installer about any service requirements, especially if you opt for an active system.

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