(The opinions expressed here are those of the author, a columnist for Reuters.)

LITTLETON, Colorado - Scorching temperature forecasts for the western U.S. over the coming days look set to kick-start the high season for natural gas use in the California power system, when the fossil fuel is used to feed demand from power-hungry air conditioners.

July and August are historically the top months for gas-fired power generation in the California Independent System Operator (CAISO) power network, as temperatures typically peak around those months and spur higher energy demand for cooling.

But forecasts for temperatures above 100 degrees Fahrenheit (38 degrees Celsius) this week look set to result in earlier-than-usual cranking of air conditioner units this year, and sharply higher gas-fired output to sustain power supply needs. More natural gas use in power generation will in turn yield higher power sector emissions, which peaked at over 6 million metric tons of carbon dioxide (CO2) a month during last summer's cooling season, according to think tank Ember.


During the June through August period, total CAISO power demand can be roughly 25% to 30% greater than the previous and following three-month windows, CAISO load data shows, largely due to higher demand for cooling.

And while power providers are steadily increasing the amount of renewable power in the CAISO system, network operators have historically lifted output from natural gas by more than other key power sources to plug potential supply shortfalls.

The responsive and reliable nature of gas-fired power means that power suppliers can depend on it to plug both unexpected short-term shortfalls and longer-term system imbalances such as when demand jumps above normal for weeks at a time.

Between 2021 and 2023, CAISO operators boosted gas-fired power output by an average of 72% during the June to August window from the average levels of the preceding three months.

In 2024, the increase to gas use could be even higher after CAISO generators were able to cut natural gas generation in May to multi-year lows thanks to greater generation from cleaner power sources within CAISO last month.


Rapid growth in renewable energy generation has helped CAISO power suppliers cut back on fossil fuel use in recent years.

CAISO solar production has grown particularly quickly, increasing by 20% from 2021 to 2023, according to LSEG data.

From January to May 2024, CAISO solar output was a record 771,000 megawatt hours (MWh), up 27% from the same period in 2023.

Such a steep climb in solar output means solar has overtaken natural gas to emerge as the primary source of CAISO power since March.

CAISO wind power generation also exceeded natural gas generation in May 2024, and along with solar output accounted for a record 51.2% share of CAISO's total power output that month, LSEG data shows.


Clean power's share of the CAISO mix could expand even further over the near term as solar farms boost output over the sunniest months of the year.

But the intermittent nature of renewable generation means CAISO operators must keep gas production assets primed for use.

Solar production assets can provide more than 70% of total CAISO power supplies during the sunniest times of the day, but then reliably drop to generating zero power at night.

Wind farms historically hit their annual high point for generation in May and early June, but then tend to steadily decrease output in July and August due to low wind speeds at turbine level during summer.

To cushion power markets from the impact of such volatile swings in clean generation, CAISO operators are likely to deploy growing volumes of gas-fired power over the next several weeks.

In 2023, CAISO gas-fired generation jumped from just under 150,000 MWh in May to 200,000 MWh in June to more than 400,000 MWH of output in both July and August, LSEG data shows.

During July and August 2023, gas supplied over 40% of total CAISO power - far more than any other single energy source - and spewed out the highest monthly CAISO emissions tolls that year in the process.

If generation trends follow the same pattern in 2024, gas production levels will have to be cranked potentially four-fold by July from less than 100,000 MWh in May.

Such an upswing in gas-fired generation could yield a similar climb in power pollution, which in turn may further accelerate the warming trends that are driving up power use in the first place.

But until CAISO operators can build up reliable means to discharge clean power when the sun stops shining and wind speeds slow, including through batteries and other storage means, top-ups from gas-fired plants will remain the main way CAISO keeps California cool.

(Reporting by Gavin Maguire; Editing by Jamie Freed)