How much electricity does CA buy from outside of state each year?
Executive summary
California routinely imports roughly a quarter to a third of the electricity that serves the state each year, which translates to on the order of 70–90 million megawatthours (MWh) annually depending on the year and counting method (net imports); in percentage terms imports are often reported as about 25–30% of total system supply [1] [2] [3]. State and federal data show variation: earlier multi‑year averages run higher (≈89 million MWh), while single‑year snapshots commonly fall in the low‑70 million MWh range — and the California Energy Commission treats imports as about 30% of the statewide “total system electric generation” aggregator used for the state’s power mix accounting [2] [1] [3].
1. How the numbers are being counted — “imports” versus total system generation
California’s public accounting for the electricity that serves the state is the “total system electric generation,” which sums in‑state utility‑scale generation and net electricity imports reported by balancing authorities; imports are tracked from Northwest and Southwest regions and allocated to fuel types via Power Source Disclosure filings (Energy Commission methodology) [4]. That definition matters because public figures about “how much California buys from outside the state” generally refer to net imports — power delivered into California after subtracting exports — not gross transactions in both directions [4].
2. Historical ranges: tens of millions of MWh and wide year‑to‑year swings
Federal and state reporting together put California’s net annual imports in the tens of millions of megawatthours: an EIA multi‑year average for 2013–2017 lists California as the largest net importer at roughly 89 million MWh per year on average [2], while EIA’s 2019 estimate shows net imports of 70.8 million MWh, about 25% of that year’s total electricity supply [1]. Other federal snapshots — for example a 2016 daily average extrapolated to a year — produce similar ballpark totals (~73 million MWh annually) and corresponding shares near the mid‑20s percent of demand [5].
3. Recent context and a simple 2023 estimate
The California Energy Commission’s 2023 “total system electric generation” figure was 281,140 GWh (281.14 million MWh), which is the combined in‑state generation plus net imports for that year [6]. Using the Commission’s commonly cited rule‑of‑thumb that imports account for approximately 30% of total system generation in recent years gives a quick estimate of roughly 84,000 GWh (84 million MWh) of imports in a year like 2023, though the Commission and EIA present actual net‑import totals year by year rather than always publishing that derived value directly [6] [3].
4. Why the range exists: weather, hydrology, ownership and market flows
The scale of imports fluctuates because California’s in‑state output swings with weather and hydro conditions (droughts reduce hydro and raise import need), ownership stakes in out‑of‑state plants change how utilities schedule flows, and hourly market dynamics cause the state to import during some hours and export in others — all of which make single‑year figures sensitive to circumstance (Energy Commission descriptions; EIA reporting) [3] [4] [5]. The Energy Commission’s quarterly and annual balancing‑authority reports are the official data source used to calculate the net imports that feed the statewide accounting [4].
5. Environmental and policy implications tied to imports
Imported power is part of California’s decarbonization strategy but also creates tradeoffs: much of the state’s imported energy comes from Pacific Northwest hydro and Southwest thermal resources, and analyses note that some imported energy—about 10% of imports in some summaries—was generated from coal in sending regions, raising emissions and environmental‑justice concerns outside California [4] [7]. Policymakers debate whether increasing interconnections would smooth variability and enable exports of surplus solar, or risk ceding control of the state’s clean‑energy targets — a political judgment the legislature has repeatedly weighed [8].
6. What can be stated with confidence and what remains to check
It is certain from federal and California Energy Commission data that California imports on the order of 70–90 million MWh per year and that imports typically represent about 25–30% of the state’s total system electric generation; exact annual totals require reading the Commission’s year‑specific net‑imports table or the EIA state interchange tallies because the figure moves with hydrology, market conditions and multi‑year averaging choices [1] [2] [3] [6]. The Energy Commission is the primary state source for the annual net‑import numbers and methods [4].