Based on a report  of RE-DISS project , this article aims to give a succinct description of the total supplier mix and the methodology to calculate it. For more details and discussion, we refer to the RE-DISS report and the reference therein.
To see the most recent total supplier mix data, check the Facts and figures in our
country fact pages.
- Terminology and remarks
- Case I: Without international physical electricity exchange
- Case II: With international physical electricity exchange
The total supplier mix (TSM), sometimes also called electricity fuel mix, is a figure that discloses the sources from which the electricity is generated. It takes into account the international physical transmission of electricity and trading in certificates. According to Directive 2009/72/EC, electric power consumers must be informed about the origin of the electricity that they have purchased.
If all national electrical grids were isolated, the fuel mix would be simply the production mix of the respective nation. If international electricity exchange exists but all consumption was completely disclosed with explicit tracking instruments (e.g. GO), the calculation would be as simple as counting the tracking instrument (e.g. cancelled GOs).
However, the situation is neither of above, i.e. international physical electricity exchange exists, and only part of the consumption is explicitly tracked. This makes it no longer an easy task to determine the supplier mix for each country individually in a “fair” way. E.g. A problem similar to the “hen and egg” dilemma arises: Country A exports physical electricity as well as GOs to country B, while B also exports electricity and GOs to C, and finally C exports electricity and GOs back to A again.
To address this problem, the RE-DISS project proposed a comprehensive framework. The key concepts involved are “attribute” and “the European attribute mix (EAM)” - a central pool of attributes for all involved countries, both defined below. The key idea is that there exists an overall balance of attributes among the countries who trade attributes with each other. EAM is the key concept that enables us to quantify this balance and to calculate the TSM.
To illustrate, we can look at the following chart  and observe the difference between production mix and supplier mix among several countries in Europe, especially, e.g. Norway, Netherland, and Denmark.
A simple example: If one country generates and consumes electricity domestically, but sells GOs abroad. Then the consumed electricity “loses” the attribute of its origin, resulting in a deficit of attributes. The balance is recovered either by importing attributes, or (implicitly) interacting with EAM.
If all consumption is explicitly disclosed, e.g. by cancelling GOs, EAM will be void and the TSM can be calculated easily. However, only a part of the electricity consumption is disclosed explicitly, and thus resulting in much more involved calculations for the TSM.
Terminology and remarks
The following terminologies are used through this article. Here are full definitions and some discussion.
Mix- This term appears in several definitions, and it refers to a composition of something, e.g. of electricity production. It is measured in absolute unit first, e.g. GWh, and then the percentage can be derived when necessary.
Attribute- According to RE-DISS, “attribute” refers to “a piece of information which is tracked in order to disclose specific consumption”. It is created when the corresponding electricity is generated. One should not, however, equate GOs and attributes, but the former are the instrument that carries the attributes (the information).
PM- Production Mix, the composition of sources from which the electricity in one country is generated. E.g. 20 GWh from wind power, 40 GWh from fossil fuel. The PM should be adjusted accordingly when electricity is exchanged with foreign countries.
DRM Domestic Residual Mix, the attribute for each source left from PM after explicit tracking, e.g. in terms of GOs.
Consumption- it equals in amount (not in mix) to the domestic production plus import and minus export of physical electricity.
UC- Untracked Consumption, the consumption not disclosed explicitly, e.g. with GOs. So, UC = Consumption - Cancel. Note that UC does not necessarily imply a deficit of attributes. One needs to further compare it with DRM to see if there is a deficit or surplus of attributes.
EAM- European Attribute Mix, it is a pool of attributes gathered from those countries that have an attribute surplus (UC - DRM < 0) so that the countries with a deficit can (implicitly) “take” from EAM to balance their attribute account.
FRM- Final Residual Mix equals the DRM adjusted by interaction with the EAM. FRM is then regarded as the composition of the consumption that is not explicitly disclosed. FRM is proportional to the DRM for a country, if its DRM in total amount is not less than UC.
TSM- Total Supplier Mix (also called the “fuel mix”) of a country, the mix of sources from which the electricity it consumed is generated.
Case I: Without international physical electricity exchange
Starting from the PM, first the attributes are gathered to work out the DRM where the basic operations are the import, export, and the cancellation, of the attributes. Next, we see whether the DRM can cover the UC. A surplus will contribute to EAM; countries with a deficit would implicitly “take” the same amount of attributes from the EAM to cover their deficit. Adding the interaction with EAM, the FRM is found. Finally, the FRM plus cancellation gives the TSM.
Hence, the key step is comparing the DRM and the UC and subsequently define the interaction with EAM for each individual country. It is worth keeping in mind that the EAM as well as any interaction with the EAM is completely imaginary. Real transactions of attributes only happen for explicit tracking activities.
We now formulate the above process as follows
PM = Physical mix of electricity generation
DRM = PM + Imp - Exp - Cancel
Consumption = total amount of physical electricity generation in a country
UC = Consumption - Cancel
Compare DRM and UC, and build the EAM: FRM = DRM + interaction with EAM
- If DRM > UC (i.e. a surplus in attribute), add the surplus to the EAM, with same mix as the DRM
- EAM = sum of attribute surplus from all countries with attribute surplus
- If DRM < UC, deficit in attribute, then take same amount attribute from EAM, with same mix as EAM
FRM = DRM + interaction with EAM
TSM = FRM + Cancel
TSM is calculated for each country and each fuel source in terms of attributes rather than physical electricity. It is done in absolute number first, and then the mix can be easily found.
We give an example of TSM calculation, while readers are strongly encouraged to try their own ones to get more familiar with the ideas.
Consider two countries, A and B, with only two kinds of fuel sources R and N (renewable and non-renewable). A is a relatively “brown” country that does not care much about its TSM and sells some of it its renewable GOs. B, in contrast, is a country that aims for a “greener” TSM profile. Below are their “attribute balance sheets” of certain year:
Finding DRM, UC, and interaction with EAM
DRM(A,R) = 4 + 0 - 3 - 1 = 0, DRM(A,N) = 20 + 0 - 0 - 0 = 20
Since all attributes to renewable sources are either exported or cancelled, the DRM of A is simply 100% non-renewable.
UC(A) = ( 4 + 20 ) - ( 1 + 0 ) = 23
UC(A) - sum DRM(A) = 23 - ( 0 + 20 ) = 3. This results in a deficit that needs to be filled with EAM.
DRM(B,R) = 10 + 3 - 0 - 11 = 2, DRM(B,N) = 5 + 0 - 0 - 2 = 3
After international trading and cancelling of attributes, the DRM of B is 2 / ( 2 + 3 ) = 40% renewable, and 60% non-renewable.
UC(B) = ( 10 + 5 ) - ( 11 + 2 ) = 2
UC(B) - sum DRM(B) = 2 - ( 2 + 3 ) = -3. This results in a surplus which will be added to EAM according to B’s own DRM, i.e. 40% renewable, 60% non-renewable.
Before we continue: note that in general there is a balance between export and import of attributes. also a balance between surplus and deficit toward EAM.
Finding FRM and TSM
Next we want to determine the composition of the EAM. For country B there is 3*40%=1.2 renewable and 3*60%=1.8 non-renewable sources. Consequently, A gets 1.2 of R and 1.8 of N for its FRM:
FRM(A,R) = 0 + 1.2 = 1.2, FRM(A,N) = 20 + 1.8 = 21.8
FRM(B,R) = 2 - 1.2 = 0.8, FRM(B,N) = 3 - 1.8 = 1.2
This is the result of interactions with the EAM. Finally, the TSM that can be derived by adding the cancellation:
TSM(A,R) = 1.2 + 1 = 2.2, TSM(A,N) = 21.8 + 0 = 21.8
TSM(B,R) = 0.8 + 11 = 11.8, TSM(B,N) = 1.2 + 2 = 3.2
After attribute trading between A and B, the TSM of B is 11.8 / ( 11.8 + 3.2 ) = 78.7% renewable. Hence, the TSM of country B is greater than its own production mix (which is 10 / ( 10 + 5 ) = 66.7%) due to the import of attributes of renewable sources. The TSM of country A becomes even more “brown”: 2.2 / ( 2.2 + 21.8 ) = 9.2% renewable. Which is less than its production mix 4 / ( 4 + 20 ) = 17%, because the country has sold some of its renewable attributes.
Case II: With international physical electricity exchange
In the case that there is an exchange of physical electricity with neighboring countries, PM, and consequently DRM, should be adjusted accordingly. We denote APM as adjusted PM.
- P-Imp = Physical Import, same mix as PM + Imp - Exp - Cancel, i.e. DRM as if no Imp/Exp, of the source country (use PM if DRM unavailable)
- P-Exp = Physical Export, same mix as PM + Imp - Exp - Cancel of the internal country, i.e. DRM as if no Imp/Exp
- APM = PM + P-Imp - P-Exp
- Adjust DRM and denote the new figure by ADRM = APM + Imp - Exp - Cancel
- Consumption = total amount of generation + import - export, of physical electricity in a country
- Continue the same calculation with ADRM for DRM
 Numbers in the chart are based on AIB: 2015 European Residual Mix - report