About Green tariffs

This site only lists tariffs that are specified by the supplier as being 100% renewables. In some cases the supplier's fuel mix is entirely renewables, in others their fuel mix includes other sources but they guarantee to match the supply to customers on a 100% renewables tariff with electricity sourced from renewables.

Because most electricity supply goes through the National Grid there is no direct linkage between the electricity customers receive and the electricity that is generated or purchased by their supplier. Unless you generate your own electricity from solar panels or a wind turbine, then you are getting electricity from the same supply as your neighbours.

To offer a 100% renewables tariff, suppliers need to ensure they either supply to the grid at least as much renewable electricity as their customers on these tariffs consume (either through their own generation or by way of contracts with renewable generators) or they need to purchase REGO (Renewable Energy Guarantees of Origin) certificates to an equivalent amount. REGO certificates are sold by renewable energy generators who have supplied electricity to the National Grid rather than to individual suppliers.


There has been increasing discussion over the use of REGO trading by suppliers in order to meet their renewables commitment, with some going as far as calling it greenwashing.

At least one electricity supplier, which generates its own renewable electricity, argues that their tariff is superior to those that involve the purchase of REGO certificates. Their main argument seems to be that REGO certificates can, at least for now, be purchased very cheaply - meaning that the required REGOs to cover supplying a domestic property can be under 50p a year.

This suggests to us not that the concept of matching renewable output to renewable supply through a certificate scheme is invalid but rather that the market may be flawed; the result of supply and demand where renewables generation has increased from 11% five years ago to 29% in 2017-18.

Whether generation and supply is matched up through 'vertical integration' (where the generator and supplier are the same company), through contracts between generator and supplier, or through a certificate trading scheme, they all involve generators supplying their electricity into the general pot that is the National Grid, and renewables customers receiving electricity from that pot.

The link between generation from specific sources and supply to individual customers is inherently indirect. But it goes further than that, the quantities of Renewables electricity generated vary with time, and those variations are not matched to when a supplier's customers use electricity.

So whatever type of 100% renewables tariff you are on you are supplied with electricity from the Brown and Green mix that's in the grid at the time you use it. REGO certificates (be they from the supplier's own generation, direct contracts or trading) ensure that for every unit of electricity you use a unit of renewables electricity has gone into the grid, but in none of these cases is it anything other than an accounting exercise.

To portray suppliers who have their own Renewables generation or direct contracts as truly green while those who purchase REGOs as merely greenwashing is, in our view, not looking at the whole picture.

However, with such a low price for REGOs, it can be deduced that REGO trading is providing little financial support to renewables generators. And for that reason, and in the interests of transparency, we have been considering if we can include information on this in our listings.

Ideally, Ofgem would be setting down requirements on suppliers to provide this sort of information to their customers and in sales material. But given that Ofgem lets suppliers away with not even meeting their existing licence requirements on publishing basic Fuel Mix information, hoping for that would be wishful thinking.

A further consideration in assessing the Green-ness of a 100% renewables tariff is where suppliers offer 100% renewables tariffs but their overall fuel mix is not 100% renewables. In some cases this can be that they are actively growing their renewables business, but in others it is simply robbing Peter to pay Paul. For every new 100% renewables customer they get, they just give less renewables to their other customers. It is for this reason that we have taken the decision not to list any tariffs from the Big Six suppliers. For other suppliers, we give their latest overall fuel mix (and you can see these suppliers' fuel mix trends on our sister site Electricity Info) and let you decide for yourself.

What is green electricity?

‘Green electricity’' means electricity produced from sources which do not cause these impacts upon the environment. Of course, every type of electricity generation will have some impact, but some sources are much greener than others. The cleanest energy sources are those which utilise the natural energy flows of the Earth. These are usually known as renewable energy sources, because they will never run out.

Wind power

The winds that blow across the UK can be harnessed by turbines to provide electricity. Wind turbines sited in suitable locations already provide a small, but growing percentage of the UK's electricity, and are used successfully all around the world. In fact wind power is one of the world’s fastest growing energy sources! Wind turbine technology has greatly improved over the last ten years, making wind turbines quieter and more efficient so that electricity generated from the wind is now often competitive with traditional coal-fired and nuclear power stations. Wind turbines are also beginning to be built at sea — in the future much of our electricity could come from these offshore windfarms.

Solar power

Many people believe that we don't get much solar energy here in the UK. In fact solar power is already being used to provide essential power for many types of equipment being used in both remote and urban areas across the country. A solar photovoltaic (PV) module works by converting sunlight directly into electricity (even on cloudy days) using semiconductor technology. The vast majority of solar modules available today use ‘waste’ silicon from the computer chip industry as the semiconductor material. They can be integrated into buildings and even made into roof tiles virtually indistinguishable from normal tiles.

Solar energy can also be used to heat water directly using specially designed collectors. Even in winter a useful amount of hot water can be produced from roof top collectors. A third way to use solar energy is simply to design buildings to make maximum use of the sun. Using this so-called 'passive solar' approach, much of the energy that we currently use for heating, lighting and air conditioning can be saved.

Hydro power

Water turbines have been used to provide electricity for over 100 years and presently provide over 1% of the UK’s electricity. Although most of the possible sites for large hydropower stations in the UK have already been developed, there is a large potential for smaller schemes. These can either use a small dam or work as a 'run of the river' system which has a minimal impact on the local environment.

Wave power

Britain is blessed with some of the most powerful waves in the world. Many different devices have been designed over the years to try and capture some of this huge energy resource. With the proper support, wave power could provide a significant proportion of the UK's electricity needs in the future.

Tidal power

Tidal power has been used in Britain for over a thousand years — at the time of the Doomsday book over 5,000 tide powered mills were recorded. Unlike other renewable energy sources, which depend on the weather, tidal power is as predictable as the tides themselves. One way to capture tidal energy is to build a barrage across an estuary, storing water behind it as the tide rises and then releasing the stored water through turbines at low tide. Several sites around the UK could be suitable for this type of tidal system, the largest being the Severn Estuary. Another way is to use ‘marine current turbines’, which work like underwater wind turbines, harnessing tidal currents instead of the winds.


Geothermal energy comes from hot rocks deep underground. In some parts of the world steam comes to the surface and can be used to run steam turbines to produce electricity directly. In other places water can be pumped down and heated by the rocks to make steam. Geothermal energy can also be used to provide hot water and heating for buildings.


Either agricultural wastes or specially grown plants can be used as a fuel to run small power stations. As plants grow they absorb carbon dioxide (the main gas responsible for climate change) which is then released when the plants are burnt. So using biomass does not add any extra carbon dioxide into the atmosphere. Specially grown 'energy crops' provide not only an environmentally sound source of electricity, but also an important new opportunity for farmers. However, there are concerns about the sustainability of sourcing biomass from countries where forests are being cleared to make way for fast growing plants that are then used as biomass.

Landfill gas

As rubbish decomposes in the landfill sites where our household waste is dumped, it gives off methane gas. This gas can be captured and burnt in a gas turbine to produce electricity. Burning the gas does give off carbon dioxide but since methane, which is emitted from the landfill site, is in fact a much more powerful greenhouse gas it is better to burn it than to allow the methane to escape into the atmosphere. There are already many landfill gas systems operating in the UK.

Waste incineration

The UK generates an enormous amount of waste, and space at landfill sites is quickly running out. The best solution would be to recycle as much of the waste as possible, but instead incinerators are being constructed to burn the waste. In some cases the energy is being used to generate electricity. However many environmentalists are still concerned about the emission of harmful dioxins and also about the loss of a valuable resources that could have been recycled.

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