California’s 2025 Power Emissions Are Already Visible in Monthly Data

The California Air Resources Board (CARB) publishes facility emissions each November for the year before, so the count for 2025 is due next month. The US Energy Information Administration (EIA) publishes electricity generation by fuel and state every month, about two months behind. For California’s in-state power plants, the monthly series already shows most of what the annual count will.

From 2016 to 2024, covered emissions from in-state generation and cogeneration ran between 0.343 and 0.357 million tonnes for every terawatt-hour (TWh) of in-state gas generation. EIA’s data shows gas generation fell 14.3% in 2025, from 86.7 to 74.3 TWh. At 2024’s ratio, in-state power emissions fell by about 4.2 million tonnes, from 29.7 million to about 25.5 million.

The fall continued into 2026. Gas generation from January to July was 18.1% below the same months of 2025, while hydro output was 8.8% lower. Lower hydro output usually pushes gas generation up.

CARB MRR 2016–2024; CEC Total System Electric Generation; EIA Form 923 monthly data to July 2026; Climate Decode calculations.

Most of California’s in-state power emissions come from burning natural gas, so they rise and fall with the volume of gas burned. CARB’s mandatory reporting data puts covered emissions from in-state generation and cogeneration at 35.3 million tonnes in 2016 and 29.7 million in 2024. The California Energy Commission (CEC) puts in-state gas generation at 98.8 and 86.5 TWh in the same years. Their ratio stayed between 0.343 and 0.357 million tonnes per TWh in every year from 2016 to 2024, within 3% of its 0.348 average.

Exhibit 1 · In-state power emissions against in-state gas generation, 2016–2024

CARB Mandatory GHG Reporting data 2016–2024; CEC Total System Electric Generation; EIA Form 923 (2025); Climate Decode. The 2025 point applies the 2024 ratio to EIA’s 2025 gas generation.

The monthly series lines up with the annual one. EIA’s twelve months of 2024 sum to 86.7 TWh of gas generation against the CEC’s 86.5 TWh, 0.2% apart. A year’s in-state power emissions can therefore be read from EIA’s data as soon as December is published, months before CARB’s count.

EIA’s data shows 74.3 TWh of in-state gas generation in 2025, 14.3% less than 2024’s 86.7 TWh. January to July 2026 brought 30.0 TWh, 18.1% below the same months of 2025, which were themselves 19.6% below 2024. July 2026 was the only month to run above the year before (Exhibit 2).

Exhibit 2 · California in-state natural gas generation by month, 2024–2026

EIA Form 923 monthly generation by state and fuel, January 2024 to July 2026 (2026 preliminary); Climate Decode.

Hydro does not explain the fall. California’s hydro output was 4.4% lower in 2025 and 8.8% lower in January to July 2026. Utility-scale solar generation rose 13% in 2025, adding 6.5 TWh, and a further 4.7% in the first seven months of 2026. Total in-state generation from all sources fell 4.2% in 2025, by 9.1 TWh. Imported power, rooftop solar outside these figures or lower demand made up the difference.

At 2024’s ratio, covered emissions from in-state generation and cogeneration were about 25.5 million tonnes in 2025, 4.2 million lower than in 2024. That is 1.7% of California’s 256.6 million tonnes of covered emissions in 2024, from one part of one sector. Our August analysis found that electricity and transport fuel delivered 87% of California’s fall in covered emissions from 2013 to 2024; the monthly data says the electricity part is still moving.

Imported power is the part the monthly data cannot show. Electricity accounted for 41.9 million tonnes of California’s covered emissions in 2024, 16.3% of the total, and 12.2 million of that came from imports. CARB counts imports from the reports of the companies that bring power into the state, and EIA’s state generation data stops at the border. If imports rose in 2025, as the fall in in-state generation allows, part of the in-state reduction reappears as imported emissions.

• CARB’s 2025 mandatory reporting data, due in November 2026. It settles the in-state figure and the imported power figure for 2025.
• EIA’s monthly generation data. August 2026 is due at the end of October. Gas generation peaked in July in 2024 and in August in 2025, and July 2026 was the only month this year above the year before.
• Hydro conditions in 2027. In California, hydro output and gas generation tend to move in opposite directions, so a wet winter would add to the fall in gas generation and a dry one would work against it.

Climate Decode · Advisory

How much of the compliance picture can you read before CARB publishes it?

We track covered emissions sector by sector across California, Québec and Washington, and read them against monthly fuel and power data.

Sources

• CARB, Mandatory Greenhouse Gas Reporting data, 2016–2024
• California Energy Commission, Total System Electric Generation, 2016–2024
• US Energy Information Administration, Form EIA-923 monthly generation by state and energy source, January 2024 to July 2026
• Climate Decode, California’s covered emissions fell 26% (WCI series, 25 August 2026)
• Climate Decode WCI analysis, October 2026

This article is market analysis provided for information only and is not investment advice.