• 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.

• 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.

• 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.

Sooner or later, you will have to replace your hot water heater. When that time comes, you may consider replacing it with a tankless hot water heater. Tankless hot water heaters are a popular option for home-owners, but there are both benefits and disadvantages to selecting a tankless model versus a traditional water heater.

Benefits:

• They provide an unlimited supply of hot water when you want it. As their name indicates, tankless hot water heaters do not use a tank. This means that there is no need to fill a tank and then slowly heat it before you have hot water. Instead, the water is heated as soon as you demand it and for as long as you need it. That means you can shower for as long as you want to without ending with an unpleasantly cold finish.
• They are energy-efficient. Because they do not use energy keeping water hot even when it is not needed, tankless hot water heaters save energy.
• They have a longer life-expectancy than tank systems. The typical life-expectancy of a tankless hot water heater is 20 years—about 50 – 100 percent longer than tank systems.
• They offer many features and options. Some models include features such as digital displays, self-diagnostic programs, and/or remote controls that allow you to adjust the temperature.

Disadvantages:

• Potentially inconsistent water temperature. If you select a model without self-modulating temperature control, you may experience fluctuations in water temperature depending upon how much water you are using.
• Potentially insufficient hot water. Tankless water heaters heat water as you need it. However, they can only heat a certain volume at a time. If you get a system that too small, you may find that it cannot handle simultaneous demands, such as providing enough hot water for two showers or a shower and a washing machine.
• Depending upon your electricity provider, your energy-efficiency may get expensive. Whereas tank systems consume a fairly steady supply of electricity, tankless systems draw power in surges when the system is called upon to heat water. Electric companies that impose a demand charge fee may cause your electric bill to increase.

Tankless water heaters are an increasingly popular choice for homeowners. However, it is important to understand the benefits and disadvantages they offer before deciding upon the best option to meet your needs.