What are the requirements for green energy tariffs?

Energy suppliers have to provide information about the mix of fuels they use to generate the electricity they supply to customers and its environmental impact. You can see the fuel mix for each energy supplier in our Energy Suppliers section.

In addition, all green supply tariffs must:

• Be transparent and meet with the general consumer perception of what constitutes the definition of green energy.
• Provide the consumer with the satisfaction that their use of this green tariff makes a difference to the environment.
• Have supporting evidence to verify all claims and upon request make it available to the public or an external verifier.

For more information about green energy tariffs, see our Guide to Energy Tariffs.

Some tariffs are certified by the Green Energy Supply Certification Scheme. This means that they have been independently tested and found to meet the requirements set out by Ofgem's Green Energy Supply Guidelines, which guarantees that: 

• The electricity you use will be matched by renewable energy. 
• The tariff will deliver additional benefits to the environment. 
• The scheme's independent panel will ensure suppliers' continued compliance with the guidelines.

If a tariff is certified, it will say so in its notes on the Which? Switch results page. For more information, you can visit the Green Energy Scheme's website.

You can search for green tariffs using Which? Switch by the lowest price available, or by fuel mix. If you select fuel mix, your results will be displayed in order of the amount of renewable energy used in the energy supplier's fuel mix and not by price. 

The best green tariffs are offered by energy suppliers that produce more green energy than their legal obligation. The most prevalent sources of green energy in the UK are biofuels, wind and water. Unlike fossil fuels, these will never run out and do not release extra carbon dioxide (CO2). Green, or renewable, energy is generated by harnessing the power of the wind, sun and sea, or by burning replaceable sources such as waste products and crops.