Alberta’s western interties offered an average of 461 megawatts (MW) of import room across every hour of 2025, which by our arithmetic is 3.6% of the 12,785 MW record the province set on Dec. 11, 2025. The Alberta Electric System Operator (AESO) published both figures in its 2025 Annual Market Statistics in March 2026. Anyone who assumes British Columbia or Montana will carry Alberta through a cold snap should start with that ratio.
The paper ceiling is higher and still low. The AESO’s transfer path document, posted March 10, 2023, sets the combined British Columbia and Montana import limit at 1,110 MW under normal conditions, with the Saskatchewan path at 153 MW. Together that is 1,263 MW, or 9.9% of the record peak by our arithmetic.
Key facts
- The Alberta Electric System Operator’s 2025 Annual Market Statistics, published in March 2026, records an all-time peak Alberta internal load of 12,785 MW on Dec. 11, 2025.
- Average import Available Transfer Capability on Alberta’s western interties fell to 461 MW across all hours of 2025 from 547 MW in 2024, according to the Alberta Electric System Operator’s 2025 Annual Market Statistics.
- The Alberta Electric System Operator’s 2025 Long-Term Transmission Plan, published in January 2025, gives the Alberta to British Columbia intertie an import capability of 800 MW against an import path rating of about 1,200 MW, and the Montana-Alberta Tie Line an import capability of 310 MW.
- The Alberta Electric System Operator’s 2025 Long-Term Transmission Plan states that the McNeill converter, commissioned in 1989, provides 150 MW of import and export capability between Alberta and Saskatchewan.
- An Alberta Electric System Operator project overview posted June 10, 2026 sets a goal of restoring British Columbia import capacity to about 950 MW.
Why Alberta cannot pull more power through the lines it already has
The two western ties run on alternating current, so Alberta’s generators turn in step with the rest of the Western Interconnection. When a large generator inside Alberta trips, most of the lost supply arrives as a surge over those ties, which the AESO’s 2023 Reliability Requirements Roadmap calls in-rush. If scheduled imports already fill the lines, the surge has no headroom, and the roadmap describes the risk of voltage collapse and cascading trips of the interties themselves.
So the operator holds room back. The roadmap puts the largest single loss Alberta plans around at 466 MW while interconnected. Imports are then backed by customers who have agreed to be tripped off automatically, a load shed service, and by fast frequency response from resources that can inject power within moments. The transfer path document carries tables setting the minimum load shed service required for a given level of imports, up to 971 MW. The Saskatchewan tie works differently, through the McNeill converter station, and its 150 MW is small beside the western pair.
What shrank Alberta’s import room in 2025
The drop from 547 MW to 461 MW did not come from the wires. The AESO’s annual statistics say import hours were so infrequent in 2025 that some generators able to provide fast frequency response took that capability to other markets for much of the year, and lower volumes of the service dragged the average transfer capability down with them. Fewer backup units on standby meant less usable room on the same steel.
That detail matters more than any line rating. Alberta’s import capability is a function of who is signed up to catch the machine when it slips, and it moves from year to year. It is a number an operator has to earn every hour.
The same year, the doors mostly swung outward. Average exports ran at 415 MW against average imports of 66 MW, and Alberta was a net exporter to the western grid in 75.0% of hours. The eastern door was often shut outright, with the AESO recording transfer capability on the Saskatchewan intertie at zero from late 2024 until mid-June 2025 because of an outage.
Why Alberta’s supply planning has to start inside the province
The AESO’s long-term plan states it in one line: “Alberta has a weakly connected grid with three neighboring jurisdictions.” That is an engineering description. Anyone writing electricity policy from a map of Canada, drawing arrows between provinces and assuming the hydro will flow when asked, should read that sentence first and the transfer tables second. Growth in demand already runs into the constraint laid out in the argument that the grid is the bottleneck, and the interties do not widen it.
Alberta ended 2025 with 23,242 MW of installed generation, per the same annual statistics, and that fleet is what planners have to count on when the load climbs toward 12,785 MW again. The interties work like a relief valve on a pressure vessel. They protect the system in a trip, and they let surplus power find a buyer, but nobody sizes a boiler around its relief valve.
The fix on the table is mechanical. The AESO’s Alberta to British Columbia Intertie Restoration project calls for a new substation with series compensation near the 500 kilovolt line 1201L, clearance upgrades on that line and more transformer capacity at the Bennett 520S substation near Langdon. The long-term plan lists the British Columbia path’s import rating at about 1,200 MW against 800 MW of usable capability. The restoration target is about 950 MW.
Frequently asked questions
How much electricity can Alberta import on average?
Alberta’s western interties offered an average of 461 megawatts of import room across every hour of 2025, down from 547 MW in 2024, according to the Alberta Electric System Operator’s 2025 Annual Market Statistics, published in March 2026.
What is Alberta’s record electricity demand?
The AESO’s 2025 Annual Market Statistics records an all-time peak Alberta internal load of 12,785 MW on December 11, 2025. The 461 MW of average import room is 3.6% of that record peak.
What are the import limits on Alberta’s interties with BC, Montana and Saskatchewan?
The AESO’s transfer path document of March 10, 2023 sets the combined British Columbia and Montana import limit at 1,110 MW under normal conditions, with the Saskatchewan path at 153 MW. Together that is 1,263 MW, or 9.9% of the record peak. The 2025 Long-Term Transmission Plan gives the BC intertie an import capability of 800 MW against a path rating of about 1,200 MW, the Montana-Alberta Tie Line an import capability of 310 MW, and the 1989 McNeill converter 150 MW of import and export capability with Saskatchewan.
Why can’t Alberta import more power through the lines it already has?
The two western ties run on alternating current, so Alberta’s generators turn in step with the rest of the Western Interconnection. When a large generator inside Alberta trips, most of the lost supply arrives as a surge over those ties, which the AESO’s 2023 Reliability Requirements Roadmap calls in-rush. If scheduled imports already fill the lines, the surge has no headroom, and the roadmap describes the risk of voltage collapse and cascading trips of the interties themselves. So the operator holds room back.
Is Alberta working to increase import capacity?
An AESO project overview posted June 10, 2026 sets a goal of restoring British Columbia import capacity to about 950 MW.
