GTŞ (Görevli Tedarik Şirketi)
The assigned supply company (GTŞ, Görevli Tedarik Şirketi) is the incumbent electricity retailer serving customers in a Turkish distribution region who have not switched suppliers. Under Türkiye's unlicensed generation regulation, it is also the counterparty obliged to buy a rooftop solar project's surplus energy at a YEKDEM-referenced price for ten years.
The assigned supply company, GTŞ (Görevli Tedarik Şirketi), is the retailer Türkiye's electricity market regulation designates to serve customers in a given distribution region who have not switched to a competitive supplier. Every region has one, operating under a regulated tariff rather than a negotiated market price.
For solar, the GTŞ carries a second, more direct role. Article 5(2) of the Elektrik Piyasasında Lisanssız Elektrik Üretim Yönetmeliği (12 May 2019, Official Gazette No. 30772) obliges the GTŞ to purchase a project's surplus energy, whatever remains after its netting settlement, for ten years from commissioning, at a YEKDEM-referenced price set by Presidential decision. Once that ten-year period ends, Presidential Decision No. 11415 (Official Gazette No. 33279, 13 June 2026) sets the ongoing basis: 90 percent of the current YEKDEM price for licensed facilities of the same type, capped at the hourly market clearing price.
Where a project has no separate supply agreement of its own, the GTŞ's regulated tariff is also the reference rate its netting settlement falls back on for energy drawn from the grid, independent of the surplus-purchase obligation above. Since 1 May 2026 that settlement runs hourly for non-residential facilities and monthly for the residential mesken subscriber group, so the same tariff can now apply on two different settlement periods.
Why it matters for solar installers
The GTŞ is not a passive default, it is the counterparty actually obliged to buy a project's leftover surplus, and the price basis changes at the ten-year mark. Confirming both the applicable import tariff and the surplus-purchase basis per site, rather than assuming one national figure, is what keeps a feasibility model's later-year numbers honest.
Common questions
- Is the GTŞ just a default supplier, or does it play a role in solar netting?
- Both. It is the incumbent retailer for customers who have not switched suppliers, and separately, under Article 5(2) of the unlicensed generation regulation, it is obliged to buy a rooftop project's surplus energy at a YEKDEM-referenced price for ten years.
- Can a rooftop project choose a different buyer for its surplus energy?
- No. The purchase obligation sits with the project's own assigned supply company by regulation, not by contract choice, for the first ten years from commissioning.
- Does the GTŞ's purchase price for surplus energy stay the same forever?
- No. It applies for ten years from commissioning under YEKDEM-referenced pricing. After that, Presidential Decision No. 11415 sets a lower, capped basis, purchasing surplus at 90 percent of the current YEKDEM price for licensed facilities of the same type, capped at the hourly market clearing price.
