The types of solar energy explained

When it comes to green homes, solar energy has gone from being a futuristic innovation to a standard way that green homeowners reduce their environmental footprint and save on energy costs. But if you're just starting the green home planning process, you may be wondering what all the solar energy terms you've heard actually mean.

Take a look at our quick rundown of the kinds of solar energy you can use in greening your home:

Passive or active

Solar energy can be passive, meaning it is accessed directly, such as when sunlight warms a house by streaming into the windows or skylights at a certain time of day. Active solar energy, by contrast, is harnessed and enhanced by mechanical components. An example of this would be a pump-operated solar water heating system.

Passive solar energy.

Both kinds of energy can be used in the same home design—you might have solar panels on your roof, and additionally choose the site of your home to maximize natural daylighting. (See the LEED Building Orientation credit.)


Photovoltaic, or PV, is also sometimes referred to as solar electric energy. Energy from the sun is converted into electricity through solar cells, put together into larger solar panels. These are commonly placed on the roof of a home. The whole system comprises these panels, batteries, electrical components and a mounting framework.

Photovoltaic panels. Photo by Angela Jimenez for USGBC/ContentWorx.

When installing a system like this, make sure you've asked the right questions about its suitability for your needs, and that you find a qualified contractor for installation.


Solar thermal systems convert the energy of sunlight into heat rather than electricity. This technique also uses rooftop flat panels or tubes, called thermal collectors, as well as a pump that delivers heat to a water storage tank. The heated water in the tank feeds into the home's main water-heating system and is accessible when needed by the residents in the home. As a result, the house's boiler or water heater is activated less frequently, and utility bills are reduced.

Photo: REGREEN Evacuated Tube Solar Thermal.

Solar water heating can also be used for space heating, such as through in-floor radiant heating (where solar thermal-generated hot water flows through pipes under the floor). This type of in-floor heating or baseboard heating can supplement your regular heating system, but probably not replace it entirely.

This technology isn't just limited to your home—you can also use thermal solar energy to heat your swimming pool.

Solar cooling

It sounds like a contradiction in terms, but cooling your home may also be done through solar energy, using any of the above methods: passive, thermal or photovoltaic. In passive solar, you would use principles of design to minimize heat transfer, such as through cool-roof technology.

Active, thermal solar energy cools when the thermal collectors provide energy to adsorption or absorption chillers (this is mainly used in large buildings, such as businesses). With PV, the solar energy that is driving your electric usage is assisting with the electrical load of running an air-conditioning unit.

Concentrated solar power

Concentrated, or concentrating, solar power (CSP), is one kind of thermal energy. CSP uses an array of mirrors or lenses that concentrate a large area of sunlight onto a small area to create heat for power. This is a large-scale technology employed by power plants. According to the U.S. Department of Energy, one CSP plant can generate power for 70,000 homes.


Learn what federal and state incentives are available for solar