Release date: 2025-12-17

In 2024 and the first half of 2025, on Canada's three largest pipelines (Enbridge Mainline, Keystone, and Trans Mountain) remained high, supported by strong production^{Footnote 1} and the startup of the Trans Mountain Expansion Project (TMEP)^{Footnote 2} in May 2024. These pipelines transport oil from the to Canadian, United States (U.S.), and other international destinations. A capacity addition on Trans Mountain eased export constraints and improved access to tidewater and overseas markets, while Enbridge Mainline operated near full capacity, and Keystone saw a temporary decline in throughput due to an oil release incident in the U.S. and related repairs^{Footnote 3}. Combined throughputs across the three systems reached record highs in 2024 and continued to climb in 2025, setting new monthly records above 4.60 million barrels per day (MMb/d).

Enbridge Mainline

Figure 1: Monthly throughput and available capacity on Enbridge Mainline (ex-Gretna)

Source: CER, Pipeline Throughput and Available Capacity Data

Text Alternative: This combined area and line chart shows monthly average throughput and available capacity from January 2021 to June 2025 for Enbridge Mainline at the ex-Gretna key point. Notably, throughput reached a high of 3.23 MMb/d in January and February 2025.

At times, throughput can exceed reported available capacity because of changes that occur between the time available capacity was reported, and when shipments occur (for example, changes to the proportion of product types being transported, unplanned outages, and downstream constraints).

At Enbridge Mainline's ex-Gretna ^{Footnote 4}, in Manitoba, throughput averaged 3.06 MMb/d in 2024, down 0.6% from 2023 (3.08 MMb/d). Monthly throughput ranged from a high of 3.17 MMb/d in March 2024 to a low of 2.86 MMb/d in September 2024 before rebounding to 3.16 MMb/d by December 2024. Available capacity remained steady, ranging from 3.15 MMb/d (September) to 3.28 MMb/d (March), averaging 3.24 MMb/d. averaged 94.6%^{Footnote 5}.

Ahead of the TMEP startup in May 2024, the Enbridge Mainline operated near full capacity, with exceeding capacity, resulting in high levels^{Footnote 6}. As TMEP ramped up, constraints eased and apportionment dropped, briefly ending in September and October 2024, before returning to low levels in November and December 2024. Some volumes shifted to TMEP, contributing to reduced Enbridge Mainline throughput. September 2024 volumes were further affected by scheduled maintenance at major oil sands facilities^{Footnote 7}.

Enbridge lowered uncommitted joint tolls in September 2024, lowering rates from US$10.93/b to US$9.84/b for heavy crude shipments from Edmonton to Houston via Flanagan South and Seaway^{Footnote 8} pipelines. By December 2024, flows returned to 3.16 MMb/d, supported by resumed crude oil production and stronger U.S. demand.

In the first half of 2025 (January to June), Enbridge's ex-Gretna throughput averaged 3.07 MMb/d, similar to the same period in 2024. Throughput peaked at 3.23 MMb/d in January and February 2025 as colder temperatures increased the need for additional condensate to be blended into oil sands bitumen. Throughput eased to 2.93 MMb/d in June due to seasonal maintenance of oil sands facilities. Capacity averaged approximately 3.24 MMb/d with utilization at 94.8% (January 2025 briefly reaching 100%), indicating the system was close to full.

Strong early-2025 demand and stable refinery activity supported high throughput. Apportionment remained below 2024 levels and fell to zero in April and May 2025, reflecting continued easing of constraints following TMEP's startup.

Keystone

Figure 2: Monthly throughput and available capacity on Keystone Pipeline

Source: CER, Pipeline Throughput and Available Capacity Data

Text Alternative: This combined area and line chart shows monthly average throughput and capacity from January 2021 to June 2025 for Keystone. An oil release incident in North Dakota in April 2025 resulted in throughput dropping to 446 Mb/d from over 600 Mb/d.

At times, throughput can exceed reported available capacity because of changes that occur between the time available capacity was reported, and when shipments occur (for example, changes to the proportion of product types being transported, unplanned outages, and downstream constraints).

In 2024, at Keystone's international border crossing near Haskett, Manitoba, throughput averaged 624 thousand barrels per day (Mb/d), a 4.7% increase from 2023 (596 Mb/d). Available capacity averaged 626 Mb/d, ranging from 605 Mb/d in May to 641 Mb/d in March. Utilization remained high at 99.7%, with a brief dip to 97.4% in August. Following the startup of the TMEP in May 2024, the availability of new capacity on TMEP helped ease capacity constraints on Keystone. Despite this easing, the Keystone system continued to operate at very high utilization, highlighting its importance in transporting Canadian heavy crude oil to the U.S. Gulf Coast.

In the first half of 2025, Keystone throughput averaged 578 Mb/d, 7.4% below the 2024 average. Capacity averaged 620 Mb/d, with utilization averaging 94%. Monthly utilization ranged between 94% and 100%, except in April 2025 when an oil release incident in North Dakota temporarily shut down the pipeline. Operations resumed 14 April 2025, under reduced pressure, lowering April throughput to 446 Mb/d. Flows recovered in May (579 Mb/d) and June (586 Mb/d) with capacity remaining slightly constrained.

Trans Mountain

Figure 3: Monthly throughput and available capacity on Trans Mountain Pipeline

Source: CER, Pipeline Throughput and Available Capacity Data

Text Alternative: This combined area and line chart shows monthly average throughput and capacity from January 2021 to June 2025 for Trans Mountain. Capacity nearly tripled in May 2024 with the TMEP coming online, leading throughput to increase from 300 Mb/d in April 2024 to 700 Mb/d by June 2025.

At times, throughput can exceed reported available capacity because of changes that occur between the time available capacity was reported, and when shipments occur (for example, changes to the proportion of product types being transported, unplanned outages, and downstream constraints).

In 2024, Trans Mountain throughput rose significantly following the May startup of TMEP Before expansion, monthly throughput ranged from 300 to 358 MMb/d, with an average capacity of 281 MMb/d. Utilization exceeded 100% in several months, peaking at 140.2% in April 2024, as shipper nominations significantly exceeded capacity.

With TMEP in service, capacity increased to 890 MMb/d. Throughput ranged between 674 and 744 MMb/d from June to December 2024 and utilization ranged from 75.7% to 86.4%, averaging 81.7%. Throughput was 411 MMb/d in May 2024 while Trans Mountain ramped up shipments on the new capacity. The added capacity eased congestion across Canada's oil pipeline network and enabled greater access to tidewater and overseas markets. Exports from the Westridge Marine Terminal surged, particularly heavy crude destined for Asia and the U.S. West Coast, marking a shift in Canadian oil export patterns^{Footnote 9Footnote 10}. Apportionment pressures eased following the ramp-up of expanded capacity, dropping from 18-27% between September 2023 and April 2024 to zero from May onward.

In the first half of 2025 (January-June), throughput remained high and stable, averaging 729 MMb/d with a peak of 793 MMb/d in March. The March peak likely reflected shifted export flows away from the U.S. after the U.S. announced plans in February 2025 to impose tariffs on energy imported from Canada. Although the tariffs were amended shortly after taking effect in early March to exempt products that comply with the Canada-U.S.-Mexico Agreement, it is likely that they had already influenced delivery patterns for the month of March because the shipping schedule would have been set in the second half of February. Capacity remained steady at around 893 MMb/d, resulting in an average utilization of 87.7% and a high of 88.8% in March 2025 as marine exports from Westridge continued to diversify Canadian crude destinations, narrowing the price differential between Western Canadia Select (WCS) and West Texas Intermediate (WTI) and enhancing the competitiveness of Canadian oil globally^{Footnote 11}.

Every quarter, major companies are required to report monthly pipeline throughput and available capacity data to CER^{Footnote 12}. This data is available quarterly on Open Government, Pipeline Profiles, and A look at pipeline flow and capacity.