Energy in the United States is obtained from a variety of sources, although the majority came from fossil fuels in 2025: 37% of the nation's energy originated from petroleum, 36% from natural gas, and 9% from coal. Electricity from nuclear power supplied 9% and renewable energy supplied 9%, which includes biomass,…

Solar power is an important source of electricity in India. Since the mid-2010s, India has increased its solar power significantly with the help of various government initiatives.

Solar water heating (SWH) is heating water by sunlight, using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes.

Spain is one of the first countries to deploy large-scale solar photovoltaics, and is the world leader in concentrated solar power (CSP) production. Spain is also one of the European countries with the most hours of sunshine.

Solar power has a growing role in electricity production in the United Kingdom, contributing around 6.4% of the UK's annual power generation in 2025. As of 2025, on sunny days, it provides over 30% of the UK's power consumption at times.

Polycrystalline silicon, or multicrystalline silicon, also called polysilicon, poly-Si, or mc-Si, is a high-purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry. Polysilicon is produced from metallurgical grade silicon by a chemical purification process,…

Geothermal energy is thermal energy extracted from the Earth's crust. It combines energy from the planet's formation and from radioactive decay.

Open energy-system models are energy-system models that are open source. These models can also be known as open energy models or open-source energy-system models or some combination thereof.

Octopus Energy Group Limited (formerly Octopus Energy Limited and Octopus Energy Holdings Limited), known as Octopus Energy, is a British company operating in the fields of energy generation and supply. It was founded in 2015 with the backing of Octopus Group, a British asset management company.

O.Y. Nofar Energy Ltd., commonly known as Nofar Energy (Hebrew: ע.י. נופר אנרג'י בע"מ), is an Israeli renewable energy company headquartered in Kfar Saba.