The guarantee of origin auction held on 13 August 2026 closed at a marginal price of 1,62 €/MWh for solar guarantees and 1,65 €/MWh for hydro ones, although the starting price for both types was 0,10 €/MWh. On offer were 98 482 MWh of solar and 23 394 MWh of hydro guarantees (OKTE, a. s.; Guarantees of origin — Auctions section, annual page 2026, retrieved on 23 August 2026).
This text reconstructs the course of the auction from the published tables of the operator. It is not a trading recommendation, not a guide to participating, and it holds no forecast of the price of future auctions: what is set out are the dates, volumes and prices as their administrator published them.
What a guarantee of origin is and what the auction sells
A guarantee of origin is a record tied to a quantity of generated electricity, not to the electricity itself, and it is traded independently of supply. The issuer and administrator of guarantees of origin on the territory of the Slovak Republic has since 1.1.2020 been the short-term market organiser, by its own description of the system; the auction is one of the channels through which guarantees reach account holders.
What is offered at the auction is neither electricity nor supply but a registry unit: the object of trade is a guarantee tied to a source type and to the time elapsed since generation. The auction tables therefore work with two parameters at once — the source type and the „lifetime“ of the guarantee, that is how long ago the electricity it covers was generated.
The source types appearing in the tables of 2026 are three: solar, hydro and nuclear. The first two were offered with a volume, the third appeared in August 2026 only in the table of minimum prices, without a stated volume.
Who announces the auction and from which day it runs
The auction is announced by the registry administrator and the period for submitting orders runs from that day. For the auction of 13 August 2026 the announcement was dated 3 August 2026 and order intake opened on the same day; at earlier auctions intake opened at 09:00 on the day of announcement.
The gap between announcement and auction is not a constant. At the February 2026 auction it was 14 days, as at all four auctions of 2025; at the May 2026 auction it was 12 days and at the August one 10 days. Anyone planning participation on the previous rhythm is working with a shorter window than a year ago.
The auction day has a fixed internal structure. Order intake closes at 13:00 and evaluation takes place at 15:00 on the same day; this pair of times is identical across every auction of 2025 and 2026 that the operator has published.
Step by step: from announcement to evaluation
The table below captures the full course of the most recently published auction as the annual page for 2026 sets it out. It is a single cycle, from notice to the announcement of the result, with three of the five steps falling on one day and the gap between the first and the last step being ten calendar days.
| Step | Date and time |
|---|---|
| Announcement of the auction | 3 August 2026 |
| Opening of order intake | 3 August 2026 |
| Auction date | 13 August 2026 |
| Closing of order intake | 13 August 2026, 13:00 |
| Evaluation of the auction | 13 August 2026, 15:00 |
The whole cycle therefore ran ten days from announcement to evaluation, of which the last two hours covered the closing of orders and the determination of the result. The course is published on the annual auctions page for 2026.
Offered volumes and the lifetime of a guarantee
Volume is not offered as a single figure per auction but split by source type and by lifetime band. Across all three auctions of 2026 the volume was offered exclusively in the band of 6 to 9 months, although the table of minimum prices works with four bands: 0 to 3, 3 to 6, 6 to 9 and 9 to 12 months.
| Auction | Solar, MWh | Hydro, MWh | Starting price |
|---|---|---|---|
| 5 February 2026 | 98 857 | 16 851 | 0,15 €/MWh |
| 20. 5. 2026 | 27 040 | 24 440 | 0,10 €/MWh |
| 13 August 2026 | 98 482 | 23 394 | 0,10 €/MWh |
| Total across three auctions | 224 379 | 64 685 | — |
Across the three auctions of 2026 a total of 289 064 MWh of guarantees was offered, of which 77,62 % solar. Across the four auctions of 2025 it was 610 649 MWh and 81,88 % solar. The average volume per auction fell from 152 662,25 MWh to 96 354,67 MWh, that is by 36,88 %; the volumes for 2025 sit on a separate annual page.
Starting, minimum and marginal price
Three different prices appear in the tables and each of them means something else. The starting price is the value from which the given auction begins for a specific offered volume. The minimum price is stated separately for each source type and each lifetime band. The marginal price is the outcome — the value at which the auction closed.
At the auction of 13 August 2026 the starting price was 0,10 €/MWh and the marginal price 1,62 €/MWh for solar and 1,65 €/MWh for hydro guarantees, which is 16,20 times and 16,50 times the starting price. At the May 2026 auction the ratio was higher still: 1,95 €/MWh and 1,90 €/MWh against the same starting price of 0,10 €/MWh, that is 19,50 times and 19,00 times.
Minimum prices in August 2026 differed by source type, not by lifetime band: for solar and hydro they stood at 0,10 €/MWh across all four bands, for nuclear at 0,01 €/MWh across all four. The difference between source types is therefore tenfold, and within one type the minimum price does not depend on time.
Where the mechanism stops
It stops at what is published. The marginal price appears on the annual pages only for two auctions of 2026; for the four auctions of 2025 and for those of 2024 it is not on the pages. The series of marginal prices therefore has no more than two observations and no longer trend can be assembled from it.
Sold volumes are not published either. The tables state how much was offered, not how much was eventually sold, and they do not state the number of participants. From that it follows that these data say nothing directly about the level of interest — a marginal price above the starting price shows that demand exceeded the starting level, but says nothing about the size of that demand.
What this shows on the buyer’s side
The first thing the tables show is the fall in the starting price. In November 2024 solar guarantees were offered at a starting price of 0,80 €/MWh and two weeks later at 0,40 €/MWh; in 2026 the starting price fell to 0,15 and then to 0,10 €/MWh, which against November 2024 is a fall of 87,50 %. The data sit on the annual auctions page for 2024.
In 2025 the starting price held between 0,20 and 0,45 €/MWh and its movement had no single direction: 0,30, then 0,20, then 0,45 and finally 0,30 €/MWh. Only 2026 brought two consecutive auctions at the same value of 0,10 €/MWh, the lowest level in the whole published series.
The second is that this starting price is not the price the buyer pays. The denominator behind each of the ratios given is one megawatt-hour of guarantee in one specific auction, not an annual average and not the price of electricity; the marginal price of August 2026 was lower than the May one by 16,92 % for solar and by 13,16 % for hydro guarantees, which is movement between two auctions, not a trend.
Conclusions
7 November 2024 and 21 November 2024. Two auctions in one month with starting prices of 0,80 €/MWh and 0,40 €/MWh; at the first, 212 248 MWh of solar and 48 624 MWh of hydro guarantees were offered, at the second 23 650 MWh of solar.
6. 2., 7. 5., 1. 8. and 6. 11. 2025. Four auctions with a 14-day gap from announcement, with starting prices of 0,30, 0,20, 0,45 and 0,30 €/MWh and a total offered volume of 610 649 MWh. Marginal prices for that year are not published.
5 February 2026. Starting price 0,15 €/MWh, offered 98 857 MWh of solar and 16 851 MWh of hydro guarantees, gap from announcement 14 days.
20. 5. 2026. Starting price 0,10 €/MWh, offered 27 040 MWh of solar and 24 440 MWh of hydro guarantees, gap from announcement 12 days; marginal price 1,95 €/MWh for solar and 1,90 €/MWh for hydro.
13 August 2026. Announcement 3 August 2026, closing of order intake at 13:00 and evaluation at 15:00 the same day. Offered 98 482 MWh of solar and 23 394 MWh of hydro guarantees, that is 121 876 MWh in total, of which 80,81 % solar. Starting price 0,10 €/MWh, marginal 1,62 €/MWh and 1,65 €/MWh, that is 16,20 times and 16,50 times the starting price.
What changed between those dates. The starting price fell by 87,50 %, the average offered volume per auction by 36,88 %, from 152 662,25 MWh in 2025 to 96 354,67 MWh in 2026, and the gap from announcement to auction shortened from 14 to 10 days. The role of issuer and administrator of guarantees of origin since 1.1.2020 is described on the page on how the system works, where the rules are presented as diagrams, not as text.
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.