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A year of transformation on the power grid. From duck curves to battery breakthroughs, explore how California powered through 2025 with unprecedented renewable energy integration.
2025 marked a pivotal year for California's energy transition
2025 was a record-shattering year. Carbon-free energy regularly exceeded 100% of demand, and battery storage became the primary tool for managing evening peaks, fundamentally changing how California's grid operates.
California's renewable capacity has grown exponentially since 2010. Solar capacity exploded from 1.0 GW in 2010 to over 25 GW by 2025, while batteries emerged as a major grid resource only in the last few years, now providing critical flexibility with over 15 GW installed. More importantly, we continued to decrease our emissions and are on track to reach zero emissions by 2045.
Every hour of every day in 2025. Warmer colors = higher demand
Summer afternoons show peak demand, with clear daily patterns of morning and evening peaks. Winter months show lower overall demand but strong evening peaks.
The sun's daily dance across California. Dark blue to bright yellow = low to high generation
Summer months show incredible solar peaks exceeding 20 GW. Unsurprisingly, winters suffer from lower solar generation capacity factors. Note the occasional gaps from cloudy weather.
Wind patterns throughout the year
Wind generation complements solar generation in spring-summer periods, but dips together with solar during winters. Unlike solar's predictable pattern, wind shows more variability and often generates at night.
Blue = charging, Red = discharging
The daily battery cycle is crystal clear: charge during midday solar abundance (10 AM - 2 PM), discharge during evening peak (6-9 PM). The batteries are starting to help ease morning peaks as well, and charging overnight. We also witnessed batteries crossing 10GW discharge mark, helping push the use of natural gas generators down across the year.
Load minus renewables = what the grid must supply from dispatchable sources
The duck curve pattern is visible every day! Deep midday valleys (solar reducing net load) and steep evening ramps. Spring shows the most dramatic ducks due to high solar and moderate load.
Estimated hourly CO2 emissions (Metric Tons) from in-state generation and imports
Emissions closely track the "Net Load" rather than total load. Midday solar drives emissions down significantly, while evening peaks require ramping up natural gas and imports, spiking emissions.
Average market prices across all three California regions (NP15, SP15, ZP26)
Prices crater during midday solar over-supply, sometimes going negative. Evening prices spike as solar fades and demand remains high. This creates powerful arbitrage for batteries.
4-hour battery systems transformed from novelty to necessity, absorbing midday solar and powering evening peaks
Batteries charged during solar over-supply hours (negative prices) and discharged precisely when the grid needed it most - during morning and evening peaks. They show up instantly, manage the regulation with finesse. In 2026, they will be moving further into long-duration regions.
Renewable energy that could not be delivered due to local transmission constraints
California had to curtail a lot of generation, and not all of it was due to oversupply. More often, this was renewable energy that could not be delivered due to local transmission constraints (transmission lines reaching the limit of how many MWs they can transfer).
Renewable energy oversupply that was curtailed to maintain system balance
Because of very prudent solar build-out, we also observe long periods when primarily solar energy oversupply was curtailed curtailed to maintain system balance.
As the sun sets, batteries now take the first shift before natural gas ramps up
This is the new "Duck Curve" solution. Batteries (red) discharge furiously from 6-9 PM, blunting the sharp ramp that Natural Gas (grey) used to have to handle alone. This greatly reduces carbon emissions during peak hours.
How often did we hit 100% clean energy?
California's progress toward a 100% clean grid
The 57.3% figure represents the total in-state annual Carbon-Free Generation (Solar, Wind, Hydro, Nuclear, Geo, Bio) divided by Total Load. This does not include out-of-state clean generation that we import.
2025 proved that a renewable-dominated grid isn't just possible—it's happening. As battery
storage scales and solar continues its exponential growth, We will (continue to) build batteries at
breakneck speed.
Batteries will replace natural gas in regions other than evening peaks. We might see a surge in
demand from large load. Hopefully that wont derail us from our emission targets.
California is writing the playbook for the world's clean energy future.
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