One of the simplest ways for you to reduce your impact on the climate is to switch your energy supply to renewable electricity.

There is now a plethora of options available on the market for ‘renewable’ or ‘green’ tariffs, but what exactly do those terms mean? The answer is a little more complex than many energy suppliers would like to admit. 
Here is our guide to understanding renewable electricity tariffs. 

1. The cleanest energy is the energy that you don’t use in the first place 

Before we get into the detail of how renewable tariffs work, note that switching to renewable electricity shouldn’t necessarily be at the top of your carbon reduction to-do list. 

The cleanest form of power isn’t wind or solar power; it’s the power you don’t use in the first place. Prioritising energy efficiency measures that minimise your base demand will result in lower bills and resilience to volatile energy prices while making sure the electricity you’re supplied with isn’t going to waste.

2. Renewable electricity 101 

The UK’s electricity grid is supplied with power from a range of sources. Until relatively recently, most of our electricity was generated by coal and gas, but today coal has almost disappeared entirely. Filling this gap is a growing share of renewables – chiefly wind power, which overtook gas for the first time in 2023, followed by solar and a small amount of hydroelectricity. These are called ‘renewable’ because the power comes from natural sources that are unlimited in supply. Renewables are the cleanest way to produce electricity.

Read here: Power from UK wind overtakes gas in historic milestone


3. The good, the bad and the ugly of ‘green’ tariffs 

Nothing changes to your actual electricity supply when you switch to a ‘renewable’ tariff. Everyone on the grid receives the same electricity mix, regardless of the tariff they are on. Suppliers can offer these tariffs by making sure they purchase enough power from renewable sources to match the electricity their customers use. Unfortunately, some suppliers do this more honestly than others.  

The good 

In the UK, a renewable electricity generator (such as a wind farm operator) is obliged to have a special certificate called a Renewable Energy Guarantee of Origin (or REGO) for every megawatt hour of power it produces. This certificate is proof that the power generated comes from a renewable source. When a supplier purchases this power directly, they also obtain the certificate. At the end of the year, the supplier then ‘retires’ these certificates to Ofgem as proof that they have bought enough renewable electricity to cover their customers’ needs.

The not so good 

However, because of the way the market works, the electricity and the REGO certificate that comes with it can, in fact, be sold separately. And as there is far more renewable power being generated than customers on renewable tariffs, and some buyers of renewable power have no need for the certificates, there is a big surplus of certificates in the market. This means that suppliers can buy up certificates very cheaply (at a cost of about 50p each in 2020) to cover their obligations without needing to purchase any renewable power at all. 

In other words, they can have all the right paperwork to say their tariff is ‘100 per cent renewable’, all the while buying electricity from the wholesale market that includes fossil fuels, nuclear and other power sources. 

In theory, this type of tariff could still provide a valuable source of revenue for renewable electricity generators, but the extremely low cost of certificates on the market is preventing this from happening.

The ugly 

There is a strong argument that ‘green’ tariffs backed by certificates alone, whether from the UK or elsewhere, is greenwashing; customers are led to believe they are directly supporting renewable electricity when, in fact, their supplier is doing nothing of the sort.

 Read here: Key Greenwashing terms worth knowing


4. What to ask your supplier 

The most transparent way for a supplier to guarantee the provenance of their electricity is to purchase renewable power directly from generators through a contract known as a Power Purchase Agreement (PPA). PPAs give the generator the long-term certainty they need to invest in their wind turbines or solar panels while giving the end customer (you) certainty of where the electricity came from. 

To understand how ‘green’ a tariff really is, ask the supplier to provide: 

  • An annual breakdown of the electricity mix they purchase (some suppliers provide this on their website)
  • Disclosure of how much of the power they supply is backed by PPAs (and the associated certificates) and how much by just certificates alone

The more detail the supplier provides, the better. Ultimately, if a tariff looks too good to be true, it probably is. 

5. Other ways to source renewable electricity 

There are, of course, other ways to obtain a genuine renewable electricity supply. For example, there is nothing stopping businesses from arranging their own PPA with a power generator, just like energy suppliers do. One way to do this is to allow a renewable energy company to install solar PV on your rooftop under a contract to sell the electricity back to you. It may even be possible to arrange a PPA with a local renewable energy project.
Alternatively, you could install solar PV yourself, in which case you own the asset itself and have full control over the power you generate, as well as benefit from selling any excess electricity back into the grid.

6. How to report renewable electricity in your carbon footprint 

If you are formally calculating and reporting your organisation’s carbon footprint, you may understandably want it to reflect the fact that you source your electricity from renewables.  

Electricity from the grid comes under the Scope 2 category of greenhouse gas emissions. Typically, your Scope 2 is calculated based on the average carbon footprint of the UK’s electricity mix for the reporting year, regardless of the type of tariff you have. This is called the ‘location-based’ method of measuring Scope 2.

There is a second method of measuring your Scope 2 emissions called the ‘market-based’ method. This allows you to report emissions based on the specific source(s) of your electricity. In the case of a 100 per cent renewable tariff, providing it meets Scope 2 quality criteria (check with your supplier), you can technically report ‘zero’ emissions because renewables do not generate greenhouse gas emissions. 
However, while the market-based method allows you to demonstrate a positive impact on your carbon footprint, it could be misleading. The reduction in emissions you report should only be a direct result of your actions; in other words, the reduction would not have occurred without you (which is called ‘additionality’). This may be the case if your electricity is procured via PPAs with generators that do not rely on any other form of financial support (such as government subsidy). However, this is almost certainly not the case if your electricity is just backed by certificates. 
In the spirit of transparency, there are good reasons to report your Scope 2 emissions using both the location-based method and the market-based method if you have a 100 per cent renewable tariff: 

  • It provides full disclosure of the actual electricity mix you use while also showing that you have taken measures to support renewables 
  • It ensures you still have an incentive to reduce your energy consumption 

Overall, renewable electricity tariffs are a valuable tool in your arsenal for cutting emissions. But keep an eye out for greenwashing, and remember – reducing your energy usage should always come first.

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Carl Hirst MBA

Sustainability Business Advisor

In his role as a Sustainability and Net Zero Business Advisor, Carl supports businesses to boost profitability by improving resource efficiency and environmental performance. An energy and utilities professional, Carl has over 40 years' experience in energy efficiency solutions, metering and data management, utility connections, energy supply contracts, project management and waste reduction.