Sun, Wind, Water and Earth don't charge for the energy they can provide you. And there is more than enough there to cover our energy needs. Especially if we use energy efficiently.

Solar Electricity	With solar energy you can produce electricity by photovoltaics, a technology to transform light energy into electricity in silicon panels for example. It is one of the most stable and best accepted forms of producing electricity. Any roof that is oriented towards the sun, towards east or towards west, is normally suitable for photovoltaics. It is good to have a connection to the grid to make sure someone can make use of the electricity from your photovoltaic system even if you are not at home and can't use the electricity for yourself. Solar electricity can also be produced by concentrating solar radiation with mirrors and then use turbines to generate electricity. This needs big installations.
Solar Thermal	Solar thermal is the easiest way to use renewable energies. Why use gas or electricity in summer to make the hot water, when it's enough to let the water flow on top of your roof to get heated by the sun? It's relatively cheap to install and relatively small (4-6 m2 are usually enough for a 4 person family), and can be combined with almost any other hot water system. Larger panel areas can also help to heat the building, although you will normally need another heating system such as wood heating or a heat pump to allow heating also on cold winter days with little sun. There is, however, also the possibility to cover a heating demand of an entire building only with solar thermal energy, if the capacity to store heated water into the winter is sufficiently large. Solar heat can also be used for cooling purposes, by making use of the energy in it to drive a cooling system.
Geothermal Heat Pump	In winter, the underground is usually warmer than the ambient air. Tubes put into the ground combined with heat humps help to extract that heat and bring it into your house. On hot summer days, geothermal heat pumps can also be used to cool the house, by transferring heat from your house into the underground and bringing back cold water.
Aerothermal or Hydro­thermal Heat Pump	Heat pumps can also extract heat from the ambient air, or from underground water. This works well, even if it is colder outside than in your building. You do need some electricity to pump the heat, but due to physical laws of thermodynamics you can get around 3 times more energy into the house from the surrounding than what you put into the heat pump with electricity.
Other Geothermal Energy	Geothermal heat pumps are not the only way to make use of the energy from the underground; geothermal energy can also be used to produce electricity by drilling deep into the earth to reach high temperatures, or heat from hot geothermal water sources can be used without heatpumps.
Wood Energy	Biomass such as wood is a renewable form of energy, because it continously grows in the forest. In nature, old wood decays and rots in the forest. Instead you can remove wood contionously and use that wood for heating at your home or to produce electricity in larger installations.
Other Bioenergy	There is a wide range of other forms of biomass than wood: organic waste from food industry or agriculture, manure from animals, meat offals, and organic waste from gardens, kitchen in restaurants or private households, green areas or landscape management. Such organic waste can be turned into an energy-rich gas in biogas reactors, which can be used to generate electricity or to inject that gas into the gas grid, replacing 'natural gas', which is a fossil fuel. Biomass can also be used to produce biofuels. Surfaces in agriculture that are not used for food production can be used to produce bioenergy crops, which can be used similarly as organic waste.
Hydro	Water running in a river contains a lot of energy. This energy can be used to run one of various forms of turbines to generate electricity. It needs to be ensured that hydropower plants respect the natural aquatic environment.
Ocean Energy	Wave and tide energy can be used to produce electricity. While there have already been tidal power plants long ago, ocean energy is getting renewed attention these days.
Wind	Wind turbines are usually big installations, which can produce a lot of electricty. A single turbine can be enough for a thousand households. There are, however, also possibilities to harness wind power in small scale wind turbines.
Energy Efficient Building	The easiest way to reduce greenhouse gas emissions is to use less energy by insulating the building you are living in, and therefore use less energy. Such measures are highly cost-effective. Over the lifetime of a new insulation, you can save usually more costs of energy than what you have paid for the insulation. The key to compare energy efficiency in buildings is the heat consumption per square meter. Of course, in colder climates more heat is needed, even for efficient buildings. A building having an energy need for heating of less than 100 kWh ('kilowatthours') per square meter can usually be considered to be an efficient building. There is almost no limit to the energy efficiency of buildings, energy consumption for heating can be reduced to zero or almost zero (nearly zero energy buildings). Highly energy efficient houses typically have an energy consumption of less than 30 kWh per square meter.

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