An Introduction to Clean Energy: Facts and Information

Read up on better, cleaner ways to meet your energy needs by learning the basics of energy efficiency and renewable energy.

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Clean energy is simply the energy derived from energy-efficient measures and renewable energy sources. Power up your clean energy know-how with our glossary of terms and energy efficiency pyramid.

Air sealing

The process of sealing leaks to prevent the passage of air or vapor, including the use of caulk and weatherstripping. Air sealing is a cost-effective way to cut heating and cooling costs.

Electric energy

The generation or use of electric power by a device over a period of time, expressed in kilowatt-hours (kWh), megawatt-hours (MWh), or gigawatt-hours (GWh).

Energy conservation

The practice of using less energy, either by greater energy efficiency or by using less of an energy service.

Energy efficiency

Using less energy, or reducing energy consumption, to attain the same amount of useful output.


A product with an ENERGY STAR® rating means that it meets certain federally mandated guidelines regarding energy efficiency.

Geothermal energy

Natural heat within the earth that can be used to heat buildings and generate electricity.


Material used to provide resistance to heat flow, thereby lowering heating and cooling costs and improving comfort.

Renewable energy

Energy from a source that is not depleted when used, such as solar and wind.

Solar energy/solar power

Energy from the sun that is converted into thermal or electric energy.


The practice of protecting a building and its interior from the elements and making it more energy efficient.


Products like caulk, foam, tape, and vinyl used to seal air leaks around movable and stationary building components.

Wind energy/wind power

The use of wind to generate mechanical power or electricity.

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Our home energy efficiency pyramid can help you prioritize energy upgrades to improve the energy performance of your home. Start with the easiest and least-expensive upgrades on the bottom of the pyramid and work your way up!

Home Energy Efficiency Pyramid - Renewable Options, Windows, Heating and Cooling, Water Heating, Insulation and Ventilation, Energy Star® Appliances, Air Sealing, Lighting ,No-to Low-Cost Options, and Understanding and Analysis