Markets · Analysis

LADWP now buys and sells power by the minute across the West

The city's utility joined a shared real-time market in 2022. Here is what that quietly does to LA's grid, and what it does not do to your bill.

BY THE RENEWABLE ENERGY LA EDITORS · FILED OCTOBER 17, 2026 · 6 MIN READ ·

What trading by the minute actually means

The Western Energy Imbalance Market, usually shortened to WEIM, is a shared real-time market. Every five minutes, a CAISO computer looks across the western states for the cheapest available electricity to cover the small, last-minute gaps between what each utility planned for and what its customers actually use. LADWP takes part as a balancing authority, the entity responsible for keeping supply and demand matched second by second inside its own territory.

For LA, the value lands at two moments. Around midday, when desert and rooftop solar can produce more than the basin needs, the market lets LADWP sell or shed that surplus instead of wasting it; at the evening ramp, when solar fades and demand peaks, the city can pull in wind from the Rockies or hydropower from the Pacific Northwest rather than starting a local gas unit. How often that actually happens, and how much it saves, varies by season and weather.

The honest math on savings

CAISO publishes a benefits report every quarter that estimates what the market has saved its members. Across all participants, the reported gross benefits run into the billions of dollars since the market opened in 2014, with LADWP's share a smaller and more recent slice, at last public report. Treat those figures as estimates of avoided costs, not as money that lands back in your mailbox.

You will not find a WEIM line on your statement. Most of an LADWP bill covers fixed costs, the poles, wires, crews, and long-term power contracts that do not change minute to minute, and real-time trading only trims the wholesale cost of power at the margin. That saving is real but modest, and it gets blended into rates alongside everything else. If anyone promises you a specific dollar figure from this market, be skeptical.

Who is in the room, and who is not

Running the market is CAISO's job, but joining it is voluntary and limited. More than a dozen balancing authorities now take part, from utilities in Washington and Oregon down through Arizona and into the desert Southwest, which is what gives LA access to such a wide pool of wind, sun, and water. LADWP did not hand control of its system to CAISO; it still runs its own grid and answers to its own board, not to the state commission that oversees the big investor-owned companies.

Next on the horizon is the day-ahead market. CAISO is rolling out an Extended Day-Ahead Market, known as EDAM, that would let members trade a full day in advance rather than only in real time. Whether LADWP commits to it, and when, is not settled as of this filing, and the schedule for western utilities has moved before.

Worth watching this month

1. CAISO's next quarterly WEIM benefits report, usually posted a few weeks after a quarter closes, which will carry the latest estimated savings and is routine but worth a look.

2. LADWP board meetings, held roughly twice a month, where power-supply and market items show up on the public agenda.

3. Any decision by LADWP on joining CAISO's Extended Day-Ahead Market, which would matter more than a single quarter's numbers.

4. The evening ramp on hot, dry Santa Ana days, when demand spikes and the real-time value of the market is easiest to see.

5. Updates to NREL's LA100 study and the city's 2035 clean-energy target, slow-moving but the backdrop to all of this.

Where this dispatch reads

California ISO, Western EIM, www.westerneim.com, The grid operator's hub for the real-time market, including the quarterly benefit reports.
California ISO (CAISO), www.caiso.com, Operator of the Western EIM and the coming day-ahead market; market notices and maps of participating balancing authorities.
Los Angeles Department of Water and Power, www.ladwp.com, Board agendas, power content labels, and power-supply filings for LA's municipal utility.
NREL, LA100 study, www.nrel.gov/analysis/los-angeles-100-percent-renewable-study.html, Federal lab's roadmap for LA's 2035 clean-energy target (.gov).
U.S. Energy Information Administration, www.eia.gov/electricity, Federal data on LADWP's size and power sources (.gov).

Questions readers have asked

Did my bill drop when LADWP joined the market?

Probably not in any way you can see on the statement. The market trims wholesale power costs at the margin, but your bill is mostly fixed delivery and contract costs, so any savings are small and blended into the rate.

Is WEIM the same as California's main grid market?

No. WEIM is a voluntary, real-time imbalance market. LADWP still owns and operates its own grid and sets its own rates through its board, and it has not joined CAISO's full market.

Does trading with other states mean LA burns more fossil fuel?

Not usually. The market hunts for the cheapest power available every five minutes, which is often surplus solar, wind, or hydro elsewhere, and that can cut how much local gas LA has to run.

Where can I check these numbers myself?

CAISO posts its quarterly WEIM benefit reports online, and LADWP's board agendas and power-supply filings are public on the utility's site.