Natural gas is a fossil fuel and is not considered a renewable energy source.

Energy-efficient appliances consume less energy, leading to lower utility bills and reduced environmental impact. They also often provide increased comfort through features such as better insulation and temperature control.

Nuclear power plants generate electricity using nuclear fission, which is not considered a renewable energy source.

Photovoltaics is the process of converting sunlight directly into electricity using semiconductor materials.

Oxygen is not a greenhouse gas, as it does not trap heat in the atmosphere.

Renewable energy sources such as solar and wind can be intermittent, meaning they are not always available when needed. They can also have a higher initial cost compared to traditional energy sources. Additionally, some renewable energy technologies may have environmental impacts, such as the use of land for solar farms or the impact of wind turbines on birds.

Hydroelectricity is the process of generating electricity from the energy of flowing water.

Energy-efficient lighting typically uses less energy to produce the same amount of light output as traditional lighting.

Geothermal energy is the process of generating electricity from the heat of the Earth's interior.

Renewable energy systems are not considered energy efficiency measures, as they generate energy rather than reducing energy consumption.

Wind energy is the process of generating electricity from the kinetic energy of the wind.

Carbon offsets are not a type of renewable energy certificate, as they represent the reduction of greenhouse gas emissions rather than the generation of renewable energy.

Tidal energy is the process of generating electricity from the movement of the tides.

Renewable energy incentives are not a type of energy efficiency program, as they are designed to promote the adoption of renewable energy technologies rather than reduce energy consumption.

Solar energy is the process of generating electricity from the heat of the sun.