DSO (Distribution System Operator)

A Distribution System Operator (DSO) runs the lower-voltage distribution grid that connects end customers to the high-voltage backbone — typically 0.4 kV to 35 kV in Estonia. The role is defined in EU Directive 2019/944 Article 2(30) and implemented in Estonia via Elektrituruseadus § 3 ("võrguettevõtja"). Where the TSO moves bulk power across regions, the DSO delivers it to the meter.

Estonia

Elektrilevi, a wholly-owned subsidiary of Eesti Energia, serves roughly 87% of Estonian electricity customers across about 95% of the country's territory — approximately 63 000 km of lines and over 500 000 connection points. Smaller regional DSOs — Imatra Elekter, VKG Elektrivõrgud, Loo Elekter and a handful of municipal/industrial-estate networks — cover the rest. Tariffs are regulated by Konkurentsiamet (the Competition Authority) on a cost-plus basis.

What the DSO does

Three core duties: build and maintain the distribution grid, connect new customers (generation or consumption), and handle metering plus settlement data. The DSO does not sell electricity itself — that is the open supplier's role. The DSO's revenue comes from grid tariffs charged to every connection, regardless of who the customer's electricity supplier is.

Distributed flexibility and the DSO

As rooftop solar, EV chargers and home batteries proliferate, the DSO is increasingly responsible for managing local-grid congestion that the TSO never sees. Curtailment of microgenerators during sunny low-load hours, dynamic capacity tariffs, and behind-the-meter flexibility programmes all sit at the DSO layer. EU Directive 2019/944 explicitly recognises the DSO as a "neutral market facilitator" for these flexibility services — a role that overlaps in practice with the aggregator market.