Under Idaho Power's latest integrated resource plan, filed Dec. 30 with the Idaho PUC, the utility wants to accelerate the exit from its coal-fired resources and acquire more than 2,000 MW of renewable energy resources and 1,685 MW of battery storage over the next 20 years.

The IRP's preferred portfolio is a dramatic increase in zero-carbon emitting resources compared to its 2019 plan. In the time between the two documents, Idaho Power pledged to decarbonize its resource portfolio by 2045. It also includes converting the remaining two units at the Jim Bridger plant in Wyoming from coal-fired to natural gas-fired in 2024, and then retiring the plant altogether in 2034 [IPC-E-21-43].

The Boardman to Hemingway 500 kV transmission line remains central to the IRP's road map and is the only transmission line included in the preferred portfolio, although the utility continues working with PacifiCorp on Gateway West, which connects Wyoming to Idaho.

Idaho Power is also taking a closer look at the Southwest Intertie Transmission Project-North line to help acquire generation, based on IRP modeling, although it isn't currently part of the plan's preferred portfolio. The proposed 275-mile 500 kV line is the last of three segments running from the southern tip of Nevada to Idaho and is expected to come on line in 2024. SWIP-North, being developed by LS Power, would make it easier for Idaho Power to access California and the Desert Southwest markets.

"We'll be having more discussions with that developer," said Jared Ellsworth, a system planning engineer at Idaho Power.

The IRP modeling credited SWIP-North with 100 MW capacity in the summer and 200 MW in the winter, and found that the line could be more cost effective than B2H.

B2H is expected to start construction in 2023 and enter service in 2026. If BPA withdraws from the project—which it has indicated is likely and the 2021 IRP assumes—this would give 750 MW west-to-east capacity and 182 MW east-to-west capacity.

Battery storage buttresses Idaho Power's grid in the IRP, thereby reducing the need for more costly investments in transmission and distribution lines. It modeled four- and eight-hour duration battery systems as stand-alone resources and paired with solar.

The action plan includes 225 MW of battery storage by 2027 and 1,685 MW during its 20-year timespan.

The previous IRP included only 80 MW during its entire planning period. That plan also included 411 MW of new natural gas resources.

"In the last IRP, with more natural gas, we weren't stressing our grid as much," he said. "With this one, we're seeing that we're pretty full on our internal grid."

Energy storage resources typically are modeled at the grid level. However, the 2021 plan took a more granular approach. The preferred portfolio included 5 MW, four-hour duration battery systems at 17 specific locations.

Battery costs have also plummeted in the time between the two plans, Ellsworth said. "We've really seen battery costs and storage costs drop over the past few years, and also we're expecting to see additional cost declines" in coming years.

The plan also modeled pumped hydro and compressed air as stand-alone storage assets, but neither made it into the preferred portfolio.

Significant cost declines contributed to the huge increase in wind and solar resources between the IRPs. The 2019 version included 400 MW of solar and no wind. The latest installment recommends 700 MW of wind and 1,405 MW of solar. All of that wind capacity comes on line in 2024, and 885 MW of solar is added by 2027.

Idaho Power is a summer peaking utility, so solar-plus-storage is particularly attractive.

Additional wind power also complements California's demand, Ellsworth noted. "Hopefully, we can sell [excess] wind at night into California."

New transmission capacity, especially SWIP-North, will let Idaho Power "lean into that [market] diversity a little bit," he said.

Coal exits are sped up in the plan, which recommends converting Jim Bridger units 1 and 2 from coal to natural gas starting before the 2024 summer peak. Idaho Power owns a 357 MW share of the two units. It would exit them in 2034, according to the preferred portfolio.

The plan accelerates Idaho Power's exit from the remaining two coal-fired units compared to the previous IRP. In the latest version, it would exit its 174 MW share of Unit 3 in 2025 and its 175 MW share of Unit 4 in 2028. That is faster than the 2030 exit timeline in the previous IRP.

Getting out requires the utility to reach agreements with regulators and PacifiCorp, which owns two-thirds of the plant. Idaho Power owns the remaining one-third, or 707 MW.

"There's a lot of work that will have to be done in next few years," he said.

The company plans to exit its 134 MW share of the coal-fired North Valmy plant by the end of 2025. NV Energy owns the rest of the plant.

As more thermal-fired capacity is retired, meeting winter demand is going to become more of an issue, he said.

The IRP modeling included 77 MW of small modular nuclear reactor resources, based on NuScale's timeline to have a SMR unit fully operational at Idaho National Laboratory by 2030.

This didn't pencil out in the preferred portfolio, but the scenario that has Idaho Power being zero-carbon emissions by 2035 includes 693 MW of nuclear.

"I think it will be more cost effective once we add lots of renewable resources," but that depends on many variables, Ellsworth said.

The IRP also considered up to 350 MW of biomass generation and up to 300 MW of geothermal. Neither made it into the preferred portfolio.

The plan's scenarios included high electrification—more of it and at a faster pace. It increased the electric heat pump and electric vehicle adoption by a factor of 10. The scenario's action plan was largely the same as the preferred portfolio, which Ellsworth said was reassuring.

"If we do have high electrification, we aren't making any investments that we'll regret," he said.

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Contributing Editor

Dan has covered stories from Seattle to Tbilisi; spent time with the AP, Everett Daily Herald and Christian Science Monitor; and was twice a member of a team nominated for a Pulitzer Prize. He and his wife have three young children and live in Seattle.