Where Idaho's electricity comes from

In 2024, plants inside Idaho generated 20,035 GWh and Idaho customers bought 26,370 GWh at retail. The gap was covered by a net 8,348 GWh from other states, which is 31.7% of what the state used. Idaho has imported power every year the series covers: the imported share was 57.6% in 1990 and peaked at 71.9% in 1992. The share fell because in-state generation grew faster than use: in 1990 generation was 9,691 GWh against retail sales of 18,003 GWh. The full series are on Idaho electricity imports, Idaho electricity generation and Idaho electricity use.

Of the 20,035 GWh generated inside Idaho in 2024, EIA attributes 9,150 GWh to conventional hydroelectric dams, 6,285 GWh to natural gas, 3,016 GWh to wind, 1,018 GWh to solar, and 0 GWh to coal. The dams generated 9,115 GWh in 1990 and 9,150 GWh in 2024; what changed around them is the gas, wind and solar capacity built since. The breakdown by source and year is on Idaho hydropower generation.

The border flow figure does not say where the imported power was generated. The closest public record is ownership. Form EIA-860 lists every generator with more than one owner and each owner’s share, and Form EIA-923 reports each plant’s net generation by fuel. In 2024 Idaho Power, the state’s largest utility, held a share of two operating plants outside Idaho:

• Jim Bridger, WY: 33.33% of a coal and natural gas plant that generated 7,807 GWh, of which 4,817 GWh from coal. Idaho Power’s share of the output: 2,602 GWh.
• North Valmy, NV: 50.00% of a coal plant that generated 1,165 GWh, of which 1,160 GWh from coal. Idaho Power’s share of the output: 582.303 GWh.

Those shares add to 3,184 GWh, 2,186 GWh of it from coal. Against the net 8,348 GWh Idaho imported in 2024, Idaho Power's ownership shares of out-of-state plants equal 38.1% of net imports, and the coal part equals 8.3% of all the electricity Idaho used that year. An ownership share is an entitlement to output, not a delivery record: a utility can sell its share into the market or buy more than it owns, so this is the part of Idaho’s out-of-state supply that a public form ties to a named plant, not the whole of it.

The ownership arithmetic is a ceiling. Idaho Power’s parent, IDACORP, files an annual report with the SEC whose first section prints the utility’s power supply by source in thousands of megawatt-hours, and that table gives the utility’s own account of what its plants and purchases delivered. For 2024 it reports a total supply of 20,061 GWh: 7,203 GWh from its own hydropower plants (35.9%), 2,474 GWh from its shares of the jointly owned coal and gas plants (12.3%), 3,843 GWh from its natural gas plants (19.2%) and 6,541 GWh purchased (32.6%). The jointly owned plants are Jim Bridger and North Valmy, so the utility's figure for them, 2,474 GWh, is lower than the 3,184 GWh its ownership shares would allow: an ownership share is an entitlement, and the 10-K says Idaho Power ended its participation in coal-fired operations at North Valmy unit 1 in December 2019 and unit 2 in December 2025, while EIA's owner file still lists its half of both. Purchased power is not split by fuel in the report; from 2007 to 2022 it was split between contracts with small producers under federal law, mostly wind, solar and geothermal projects in Idaho, and other purchases. The series since 1998 is on Idaho Power power supply by source, where the latest year is 2025 at 20,395 GWh.

The two sources do not describe the same thing. EIA’s figures are for the State of Idaho: every plant inside it, every retail customer in it, and the net flow across its border. Idaho Power’s figures are for one utility whose territory is southern Idaho and a corner of eastern Oregon, and whose purchases include power generated inside Idaho by producers it does not own. The gap between the two is where Rocky Mountain Power, the northern cooperatives and the wholesale market sit.

EIA publishes no state-to-state flow table, so the origin of the rest of the net 8,348 GWh is not in any file on this site. Three things are known to sit in it without a published Idaho figure. Rocky Mountain Power, a PacifiCorp division, serves eastern Idaho from a six-state system whose plants include the other two thirds of Jim Bridger and coal and gas plants in Utah and Wyoming; PacifiCorp’s address on Form EIA-860 is Portland, so its plants are outside the ownership rule above, and its 10-K reports for the whole system, not for Idaho. Utilities and cooperatives in northern Idaho buy federal hydropower marketed by the Bonneville Power Administration from dams on the Columbia and Snake. And Idaho Power’s purchased power has no fuel attached to it in any filing. Each is a source of supply the border figure includes and no public series divides.

So the answer to the question is a number and a boundary. In 2024, 68.3% of the electricity Idaho used was generated inside the state, 31.7% came from outside it on a net basis, and the coal plants Idaho Power owns in Wyoming and Nevada account for a share of that imported power the ownership records put at 26.2%.