An Introduction to Solar Water Heaters Systems

Whether you are looking to save money on your electric bill or lower your carbon footprint, replacing your traditional water heater with a solar powered one may be a great option. This is especially true if you are building a new home or refinancing one. In those cases, certain federal tax deductions come into play. Depending upon your energy consumption, you could find that your net monthly bill actually leaves you saving more than you’re spending. Solar water heaters are available in two major categories:

  • Active solar heating. These systems have circulation pumps and controls that rely upon a traditional external power source, such as electricity.
  • Passive solar heating. These systems use 100% solar power to operate pumps, fans, etc.

Active systems are further divided into the following types:

    • Direct Circulation System. If you live in a climate where it seldom freezes, this may be a good choice. These systems compare the temperature of the water at the bottom of the storage tank with that at the top. When there is a significant difference, an electronic control activates a small pump and circulates the water through the solar collector, heats it, and then returns it to the top of the tank.
      • Pros: These are usually the most efficient heating method in warmer climates.
      • Cons: The system is not suited to climates where freezing is common.


  • Indirect Circulation System (aka Drain Back Systems). These systems use a heat-transfer fluid (i.e., antifreeze) which is pumped through a heat exchanger. The heat is transferred from the solar collector to the water.
    • Pros: A good choice for colder climates.
    • Cons: While still efficient, it is less efficient than a direct circulation system.

Passive systems are divided into the following types:

    • Integral Collector System. These systems do not use pumps or automatic control systems to circulate water. Additionally, the water storage and energy collection units are combined into one component, which means it cannot be insulated (otherwise, the solar heating would not reach the water).
      • Pros: A very simple system that is both small, has very few parts that can fail, and is very efficient.
      • Cons: Nighttime heat loss can be problematic in cooler temperatures. Not suitable for areas prone to freezing.


  • Thermosyphon System. This system also forgoes pumps and automatic controls. However, the solar collector and storage tank are separate. The hot water storage tank is located higher than the solar collector, typically on a roof. The solar collector heats water below the storage tank and then the hot water naturally rises to the top.
    • Pros: Because the storage tank is separate from the solar heating unit, the tank can be insulated.
    • Cons: The tank on the roof can be unsightly.

Solar water heaters are increasingly becoming a popular way to save money and help reduce the impact to the environment. With only two major categories to choose from and only two types within each category, it’s easy to narrow your choices to one that works best for you.