What is Itaipu Binacional?

Direct answer: Itaipu is a hydroelectric dam on the Paraná River, on the Brazil-Paraguay border, in commercial operation since 5 May 1984. It is binational because it is owned in equal parts by both countries, under the Itaipu Treaty, signed on 26 April 1973. Ownership is 50/50, but consumption is not: in the daily measurement from Brazil's grid operator ONS, most of the electricity generated goes to the Brazilian system, because Paraguay does not consume its half and transfers the surplus.

What the dam is

Itaipu sits on the Paraná River, on the border stretch between Foz do Iguaçu (Brazil) and the Hernandarias and Ciudad del Este area (Paraguay). It has 20 generating units of 700 MW each, totalling 14,000 MW (14 GW) of installed capacity. The original project called for 18 units; the last two came online in 2006 and 2007.

Why "binational"

Because it is neither a Brazilian nor a Paraguayan company: it belongs to both nations at once, in a 50% each partnership. That split was created by the Itaipu Treaty of 26 April 1973, which allowed the joint use of a river shared along the border.

The figure that explains the story

Here is the point most write-ups leave out. Ownership is half and half, but the energy delivered to each country is not.

We track Itaipu's generation through the hourly series from ONS (Brazil's National Electricity System Operator). In the measurement for 9 September 2026, the dam generated 237 GWh in the day, with a peak of 12,648 MW, and the split came out at 67% to the Brazilian system and 33% to the Paraguayan one.

This is not a distortion or a favour: Paraguay's electricity market is far smaller than its half of Itaipu. What it does not consume is transferred to Brazil, for payment. That transfer, and what it is worth, is the heart of the discussions between the two countries.

Annex C, where the accounting happens

The Treaty has annexes, and Annex C sets the financial terms: the energy tariff, payment for the transfer of the Paraguayan surplus, and amortisation of the construction debt. It was due for review, and its terms have been under negotiation between the two governments. Because the text depends on agreement between the countries and approval by their respective Congresses, the figures shift as talks advance: check recent news before quoting numbers.

The reservoir is measured too

Alongside generation, we track the reservoir's hydrological data through ONS. In the reading for 10 September 2026, the level stood at 219.25 metres, with an inflow of around 9,819 m³/s and zero spilled flow, meaning the spillway was closed.

Worth remembering: Itaipu is on the Paraná River and does not control the Iguaçu River, which is what feeds the falls. A flood at the falls has nothing to do with the dam.

Can you visit?

Yes, and it is one of the most popular excursions in Foz. Residents of the neighbouring municipalities get free entry to several tours: see who gets discounts at Foz attractions.

Sources: Itaipu Treaty (1973) and Itaipu Binacional · Marco Três's own series for generation and reservoir drawn from ONS, Brazil's National Electricity System Operator · verified 11/09/2026.