Chile's power generation in September: 83.6% renewable, thermal halves and hydro leads again

In September 2026, 83.6% of the electricity generated on Chile's National Electric System (SEN) came from renewable sources: water, sun, wind and geothermal. Generation from coal, gas and diesel fell to 16.4%, half of its share a year earlier, according to the monthly report of the Coordinador Eléctrico Nacional (the national grid operator) published on October 27 and summarized by REDIMIN on October 30.

Water explains the shift. Hydropower rose from 1,733 GWh in September 2025 to 2,668.1 GWh in September 2026, up 54%, and became the country's leading source again with 39.3% of generation. Total output barely moved: 6,788.9 GWh, 0.4% more than a year earlier.

With more water and more sun, thermal plants, the most expensive to run, stayed offline for much of the month. Their output fell from 2,254.8 GWh to 1,115 GWh, a 50.5% drop, and energy marginal costs fell between 35% and 67% across most of the country.

The table summarizes each technology's contribution in September, compared with the same month of 2025 where the report provides it.

Source: Coordinador Eléctrico Nacional, September 2026 monthly report, via REDIMIN. Solar's share in September 2025 was 26.1%. Within thermal, coal generated 557.9 GWh (8.2%) and natural gas 325.3 GWh (4.8%); the rest came from cogeneration, biomass, biogas and diesel.

Within hydropower, reservoir plants produced 1,758.7 GWh (25.9%) and run-of-river plants, which use river flow without large dams, 909.5 GWh (13.4%). Solar and wind together supplied 2,986.1 GWh, 44% of the total.

The thermal drop is the steepest so far this year, but the report itself notes that the plants have not been retired: they remain available and come back when water runs low, when the wind drops or when the system needs them for security, for example to control voltage in areas far from the main nodes.

A single month does not define the hydrological year either. The grid operator had classified April 2025 to March 2026 as a dry year, with an exceedance probability of 61.8%. September's jump reflects a winter with more rain and snow in central Chile, visible in reservoirs and rivers.

Installed capacity reached 41,314.9 MW at the end of September, including 1,625 MW in testing. Solar is the largest technology by capacity, 14,081.15 MW (34.1%), followed by thermal (30.6%), hydro (18.2%) and wind (16.9%). In other words, the sun leads in capacity, but in September water generated more energy.

The National Energy Commission (CNE), using its own methodology, reported in its latest sector report that non-conventional renewable energy (NCRE, which excludes large hydro) reached 20,579 MW, 53% of installed capacity, with 12,754 MW of solar and 6,314 MW of wind, according to Electrominería. NCRE plants injected 3,431 GWh in September, half of the month's generation. The grid operator's and the CNE's figures differ because they count plants on different bases.

The marginal cost is the price at which energy is valued at each node of the system every hour, and it is set by the most expensive plant running. When water and sun are abundant, thermal plants drop out and the cost falls. In September it fell at every main node in the north and center, with one exception in the south.

Source: Coordinador Eléctrico Nacional, via REDIMIN. Changes are as reported; with rounded values, some percentages differ slightly. REDIMIN does not publish the September 2025 cost at Crucero and Pan de Azúcar.

Puerto Montt is the exception: its cost rose 31.7%, to US$46 per MWh. It is the same transmission bottleneck that, according to the energy minister, explains why electricity bills in Los Ríos and Los Lagos would not fall in 2027: lines to the south lack the capacity to carry cheap power from the north. October's low prices at the Polpaico node, which we analyzed in our story on the lowest marginal cost since 2002, confirm the trend.

A lower marginal cost does not translate directly into a cheaper electricity bill. Households pay prices set in long-term contracts and in regulated tariffs, adjusted by decree every six months. Where it matters is for generators selling on the spot market and for unregulated customers with indexed contracts.

What comes next for hydropower depends on the snow stored in the Andes, which melts between spring and summer and feeds rivers and reservoirs. The news is good for central Chile and the Norte Chico. According to the hydrometeorological bulletin of the Dirección General de Aguas (DGA), with data as of October 26, cited by Reporte Minero, snow depth is 55% above the 1991-2020 average, and snow water equivalent 58% above.

Source: DGA, hydrometeorological bulletin with data as of October 26, 2026, via Reporte Minero. Average snow water equivalent reached 618 mm.

There is an important caveat for the power system: the large reservoir plants are in the Maule and Biobío basins, such as Colbún, Pehuenche, Ralco and Pangue, and stations there show deficits: -55% at Lo Aguirre and -75% at Alto Mallines. The largest surplus is in Coquimbo and Valparaíso, where less hydro capacity is installed. How much water improves results was visible in Colbún's third-quarter profit, which nearly tripled thanks to more water.

More renewables also mean more energy that cannot be used. According to the Chilean Renewable Energy and Storage Association (ACERA), solar and wind curtailment, energy lost because the grid cannot take it, totaled 3,546 GWh between January and September 2026, 4.6% less than in the same period of 2025, but still a large volume.

Batteries are the fastest-growing answer: as of September, Chile had 3,125 MW of storage in operation, with 13,555 MWh of capacity, and another 5,130 MW (22,123 MWh) under construction, according to ACERA. Those batteries store midday solar power for the night, when thermal plants used to supply it. We analyzed their growing role in our story on batteries' contribution to Chile's electricity.

How much renewable electricity did Chile generate in September 2026?

83.6% of the total, according to the grid operator: hydro (39.3%), solar (28.4%), wind (15.6%) and a small amount of geothermal. Thermal supplied 16.4%.

Why did thermal generation fall so much?

Because there was much more water: hydropower rose 54% from September 2025. With demand almost flat, hydro and solar displaced coal and gas plants, which are more expensive to run.

Will electricity bills fall because of these marginal costs?

Not directly. Household tariffs depend on long-term contracts and tariff decrees. Marginal costs mainly affect generators and large customers with indexed contracts.

What does the snowpack say about the summer?

The DGA reports a national surplus of 58% in snow water equivalent as of October 26, concentrated in Coquimbo and Valparaíso. In Maule and Biobío, home to the large reservoirs, several stations show deficits.