What the choice of denominator does to the renewable energy share

What is the share of renewable sources in Slovakia? The question looks like a question about one number, yet the annual energy balances of the statistical office for 2024 yield six different values without a single estimate: from 4,12 % to 23,14 % (ŠÚ SR, report Energ 7-12; DATAcube, tables en2002rs and en2003rs, both updated 19. 12. 2025).

This text is a calculation from zero out of two public tables, not an assessment of policy and not advice on reporting. It does not state the official rate under the renewable energy directive — that is calculated by a different method and does not appear here; what is set out are own shares and every assumption they rest on.

The question: what a renewable energy share means

A share is a fraction and a fraction has two sides. The numerator holds some quantity relating to renewable sources, the denominator some quantity relating to the energy sector as a whole, and both can be chosen in several ways. Until it is said which two lines of the balance are being divided, the number is not verifiable.

The energy balance offers at least four natural candidate levels: primary production, gross inland consumption, input to transformation and final consumption. Each of them measures something different and each exists in a renewable and in a total version. There is therefore more than one combination and all of them are arithmetically admissible.

The purpose of this calculation is not to pick the „correct“ value. The purpose is to show how large the spread is that arises from the choice of denominator alone, and to name at every figure exactly what is being divided by what.

The input data and where they come from

Two tables of the same source are used, in the same unit and for the same year. Table en2002rs covers renewable fuel sources and waste, table en2003rs covers fuels, electricity and heat together. Both carry the same update date in the collection index, which is the condition for dividing one by the other.

The data are taken from the machine output of table en2002rs and from the same output of the table of fuels, electricity and heat. By hand, the same values open in the DATAcube database filtered to 2024.

Step 1: checking whether both balances close

Before dividing, it has to be known whether volume was lost in the lines. The check is made inside each table separately and needs no external input: gross inland consumption should come out as primary production plus imports minus exports plus the change in stocks, and final consumption should come out after deducting transformation, reclassification and losses.

In the table of renewable sources: 67 955 + 6 349 − 5 279 − 148 gives 68 877, which is the published gross inland consumption. Then 68 877 − 24 219 − 8 753 − 16 gives 35 889, which is the published final consumption; the value 8 753 is the line of product reclassification and 16 are the losses in transmission and distribution. The sum of the two sector lines, 18 894 for industry and 16 995 for other activities, gives the same 35 889.

In the table of all carriers, final consumption of 416 451 splits into final non-energy consumption of 36 651 and final energy consumption of 379 800. Both tables therefore close without a remainder and dividing one by the other requires no assumption about missing lines.

Step 2: what sits in the numerator

The numerator is not clean renewable energy. Table en2002rs is called the balance of renewable fuel sources and waste and it holds no separate line for waste. Anything divided out of it therefore contains energy from waste as well, and that has to be said at every resulting figure.

The second limitation of the numerator is structural. The line „Transformation — output“ is empty in this table across the whole series from 2001 to 2024: electricity and heat generated from biomass are not tracked in it as output. Final consumption of 35 889 TJ is therefore the direct consumption of renewable fuel at the end user, not the total renewable energy the user receives — the part that reaches them as electricity or heat sits in the second table under electricity and heat.

The third limitation concerns transport. The line „Final energy consumption in transport“ is empty in the renewable table across the whole series, so no statement about biofuels in transport can be derived from these figures and none is made here.

The internal composition of the numerator is meanwhile very uneven. Of the final consumption of 35 889 TJ, 18 894 TJ falls to industry and 16 995 TJ to other activities; inside industry, pulp, paper and printing account for 9 692 TJ, that is 51,30 % of industrial consumption of renewable fuels. Inside other activities, households account for 15 396 TJ, that is 42,90 % of the whole final consumption of renewable sources, while trade and services account for only 616 TJ. A share calculated from this numerator is therefore largely a share of two groups: paper mills and households.

Step 3: the choice of denominator

The denominator decides which question the figure answers. If the denominator is the final energy consumption of all carriers, the answer speaks about how much of the energy delivered to the end user is directly burnt renewable fuel. If the denominator is primary production, the answer speaks about how much of domestic extraction and collection of energy is renewable — and that has nothing to do with delivery to the user at all.

The difference between those two questions is decisive for a country with high imports. Imports of all carriers stood at 559 357 TJ in 2024 against domestic primary production of 293 637 TJ, so imports were 1,90 times the domestic production. A share calculated from primary production therefore measures the structure of the domestic source, not the structure of consumption.

The third possible level, gross inland consumption, lies between them: it holds imports and exports, but still sits ahead of transformation and losses. The fourth, input to transformation, measures only what goes into power plants, heating plants and other conversions — and for renewable sources it is the least favourable view, because a large part of biomass is burnt directly, without transformation.

A fourth option that appears in discussions is to add the input to transformation to the renewable final consumption and divide that by gross inland consumption. The result of that combination appears in the sensitivity table below, but it mixes two different levels of the balance: final consumption is measured behind the electricity meter and the gas meter, the input to transformation ahead of them. As a rough indicator it holds; as an exact share it does not.

The result: 9,45 % for 2024

The base variant of this calculation divides the final energy consumption of renewable sources and waste by the final energy consumption of all carriers: 35 889 ÷ 379 800 gives 9,45 %. That figure answers the question of how much of the energy delivered to the end user in Slovakia in 2024 was directly consumed renewable fuel and waste.

It is a lower bound, not the whole picture. Renewable electricity and renewable heat that pass through transformation are absent from this numerator and present in the denominator — as electricity and heat. Adding the transformation input of 24 219 TJ to the numerator would be an error, because input is not the same as output and the transformation efficiency is not stated in the table.

The same calculation for earlier years gives 12,01 % in 2021, 11,67 % in 2022, 10,53 % in 2023 and 9,45 % in 2024. Over three years the value therefore fell by 2,56 percentage points, while the numerator itself fell from 52 559 TJ to 35 889 TJ, that is by 31,72 %, and the denominator fell from 437 540 TJ to 379 800 TJ, that is by 13,20 %. The numerator fell faster than the denominator, and so the share fell too.

The series cannot, however, be extended backwards at will. Between 2018 and 2019 the renewable table holds a break: final consumption rose from 27 738 TJ to 51 281 TJ and the household line rose from 1 654 TJ to 24 309 TJ, that is to 14,70 times its level, in a single year. The note attached to the table gives no reason and none is written in here; the practical consequence is that values from before 2019 cannot be compared with later ones and are not used in this calculation.

The sensitivity table: six shares from the same two tables

The overview below shows what happens to the result if the numerator or the denominator changes. All six rows use exclusively the values from the input table above, all of them relate to 2024, and none of them holds an estimate or a unit conversion. The order of the rows runs from the narrowest definition of consumption to the broadest definition of the source.

The distance between the lowest and the highest variant is 19,02 percentage points. The highest value, 23,14 %, meanwhile has nothing to do with consumption: it measures only what part of domestic primary production is renewable, and in a country importing 1,90 times its domestic production that is about something else entirely.

The sensitivity has a time dimension too. The variant with primary production gave 29,23 % in 2021 and 23,14 % in 2024, that is a fall. The variant with the input to transformation gave 4,07 % in 2021 and 4,12 % in 2024, that is a slight rise. The same year, the same tables, two opposite directions — depending on what is divided.

The sensitivity to the denominator has a third dimension, easy to overlook inside one country: imports. The denominator „primary production“ is 293 637 TJ, the denominator „gross inland consumption“ is 660 133 TJ, that is 2,25 times as much. The difference between them consists mainly of imports of 559 357 TJ reduced by exports of 207 560 TJ and adjusted by the change in stocks of 14 699 TJ. A share from the first denominator speaks about what the country produces, a share from the second about what the country consumes — and for Slovakia those are two very different quantities.

What this calculation is not

It is not the official measure of the renewable share. That is calculated under the methodology of the European directive, with its own rules for transport, heat and electricity, its own treatment of waste and its own statistical base; it does not appear here and cannot be compared with the figures above.

Nor is it a measurement of renewable electricity. The renewable table has no filled line for transformation output, so it says nothing about how much electricity was generated from biomass. Anyone needing electricity by technology needs a different data source.

Nor is it a comparison with neighbouring countries. The same two tables do not exist in this form for another state and international comparison is made through harmonised datasets, not through national balances; any of the six variants would, if carried to another country, require checking whether the same lines are filled the same way. No international comparison is therefore made here.

And finally, it is not a telling figure about an individual building. The balance is national, the unit is a terajoule per calendar year, and none of the shares given can be carried over to a specific hall, municipality or metering point.

Conclusions

The base result is 9,45 % for 2024. The denominator is the final energy consumption of all carriers, 379 800 TJ, the numerator the final energy consumption of renewable fuel sources and waste, 35 889 TJ. The figure measures directly consumed renewable fuel, not the total renewable energy delivered to the user.

The spread from the choice of denominator is 19,02 percentage points. The same two tables for the same year give 4,12 % at the input to transformation and 23,14 % at primary production. Anyone stating a „renewable energy share“ without a denominator is not stating a verifiable figure.

The direction of travel depends on the variant. The variant with final energy consumption fell from 12,01 % in 2021 to 9,45 %, the variant with the input to transformation rose over the same period from 4,07 % to 4,12 %. Both are arithmetically correct.

The numerator holds waste and lacks transformation. Table en2002rs has no separate line for waste and no filled line for transformation output, and its transport line is empty across the whole series from 2001. Those three limitations apply to all six variants equally.

All of it can be checked from two machine outputs. The values for the total balance sit in the table of fuels, electricity and heat, and the update dates of both tables are given by the DATAcube collection index. Both carry the same stamp of 19 December 2025, which is why they can be divided by each other.

Analysis, not personalised advice. Before a transaction decision, verify the tariff value or the wording of the regulation directly with the network operator or the regulator.