What a green tariff promises
A green tariff is an electricity plan that the supplier says is matched with renewable generation. Switching to one does not change the physical electricity that reaches your home. Power from all generators flows into a shared network, and no one can direct a particular wind farm’s output to a particular socket. What changes is the paperwork and, depending on the tariff, the money flowing to different kinds of generation.
That is why the exact wording of the claim matters. The idea of the electricity grid is covered in its own article. In short, what comes out of the wall is the mix on the network at that moment, whatever tariff you are on.
How suppliers back the claim
Several mechanisms are used, and they differ in how much they affect the energy system.
Certificates. Renewable generators can be issued certificates for each unit of electricity they produce. In Europe these are usually called guarantees of origin, and other regions use different names and systems. A supplier can buy certificates to cover the electricity its customers use and then say that supply is renewable. The certificates are tracked so that each unit is only claimed once.
The weakness is that certificates can be bought separately from the electricity itself. If the certificates come from old, already-profitable hydro plants, buying them may add little new renewable capacity. Some certificates are cheap, so the label can be inexpensive for a supplier to obtain.
Direct contracts. Some suppliers sign long-term power purchase agreements with specific wind, solar or other projects. These can give developers more certainty and may help new projects get built, particularly if the contracts are for newly built capacity.
Own generation. A few suppliers own renewable plants and sell the output. How much of their supply this covers varies.
Supply that is partly matched. Some tariffs cover only a share of customers’ use with renewables, and the rest comes from the general mix. This is allowed as long as it is described accurately.
Why “100% renewable” can still mean different things
Even when a claim is accurate, it may be measured in a way that is generous to the supplier.
- Annual matching. A supplier may match your yearly use to its yearly purchases, even though wind and sun vary through the day and across seasons. On a still evening, the electricity actually serving you may come largely from other sources.
- Existing versus new capacity. Backing from plants that would have operated anyway is not the same as paying for new ones. The term often used for the second is “additionality”, meaning the purchase leads to something that would not otherwise have happened.
- Location. Some claims are matched across a wide area and are not tied to the network you actually draw from.
- Different definitions. What counts as renewable can vary. Some schemes include certain forms of bioenergy, for example, which have their own sustainability debates. The various renewable energy sources do not all have the same trade-offs.
None of this means green tariffs are worthless. It means the strength of the claim differs between suppliers, and a plain “green” label does not tell you which kind you are getting.
Questions to ask
- How is the tariff backed? Certificates only, direct contracts, own generation, or a mixture?
- Does it fund new capacity? Some suppliers publish details of the projects they support or commit to investing a share of income in new generation.
- Is it 100% of your use or only part? Check the wording for percentages and time periods.
- Are the claims independently checked? An external audit or a recognised scheme adds some assurance, though schemes differ in how rigorous they are. The same caution applies to any eco-label certifications you encounter.
- Does the tariff cost more? Compare the unit rate and standing charge with your current deal, and check for exit fees. Prices change often, so compare current offers rather than assuming a green tariff is dearer or cheaper.
- How does the supplier behave overall? Whether the company also generates from fossil fuels, and its record on customer service, both matter.
If an answer is vague, that is information in itself. Our article on greenwashing claims describes common warning signs in marketing.
Alternatives and complements
A green tariff is one route to cleaner electricity at home, not the only one.
- Generating your own. Rooftop solar produces electricity at your property, though it needs upfront cost and suitable roof space, and the benefits depend on how much you use during the day.
- Community energy. Some areas have community-owned schemes you can join or invest in.
- Using less, and using it smarter. Reducing home energy use, or shifting some use to times when the grid is cleaner, can cut emissions whatever tariff you are on. Some supplier plans reward this with time-of-use prices.
- Switching what you heat and drive with. Electrification such as heat pumps or electric vehicles only reduces emissions as far as the electricity itself becomes cleaner over time, which depends on the wider system as well as your tariff.
If you are renting or in a shared building, a tariff may be one of the few direct choices available, a point covered in the article on renting sustainably.
A balanced view
Choosing a well-backed green tariff is a reasonable step and the price difference varies by supplier, but it is rarely the biggest lever available, and the benefit depends on the supplier’s approach. It is worth a few minutes of checking rather than hours, and it is best treated as one part of a wider plan to reduce energy use. If the details are hard to find or understand, that is a good reason to look at another supplier.