Ensuring future power grid reliability

This article was published by the Canada Energy Regulator on Oct. 15, 2025.

Every time you turn on a light switch, a complex system delivers electricity from power plants to your home. This system, the electric grid, includes the bulk power system (BPS) and the distribution system, and it works 24/7 to keep the lights on.

What is the bulk power system (BPS)?

The electric “grid” delivers electricity from producers to consumers. It includes the:

1. Generation system
2. Transmission system
3. Distribution system

The “Bulk Power System” (BPS) includes the generation and transmission systems. The North American Electricity Reliability Corporation (NERC) defines the BPS as “the facilities and control systems necessary for operating an interconnected electric energy transmission network (or any portion thereof); and electric energy from generation facilities needed to maintain transmission system reliability. The term does not include facilities used in the local distribution of electric energy”^Footnote 1.

Maintaining the reliability of the BPS is crucial to ensuring the overall reliability of the electric grid.

Figure 1: Bulk Power System (BPS)

BPS reliability

Most Canadian provinces follow NERC’s reliability standards. Each province is responsible for maintaining the reliability of its BPS. NERC defines BPS reliability in terms of two parts:

1. Adequacy^Footnote 2 means having enough resources to provide electricity at the proper voltage and frequency to continuously meet customer demand, virtually all the time. This is more generally referred to as resource adequacy^Footnote 3 and is evaluated at the planning stage. In this planning stage, power system planners look ahead to predict how much electricity will be needed in the future, and make sure enough power plants and other resources will be available to meet that need, including some extra capacity for emergencies.
2. Operating reliability^Footnote 4 refers to always keeping the power on—the ability of the electric system to withstand sudden and unexpected disturbances like short circuits or unplanned outages^Footnote 5. This is an issue that is managed in real time in the operational stage.

A reliable BPS is one that meets both these conditions, virtually all the time. An indicator of grid reliability difficulties is the Energy Emergency Alert (EEA). EEAs are alerts sent out by system operators during major grid events. These alerts are classified at different levels by NERC; level 3 being the most critical^Footnote 6, indicating the highest threat to grid reliability. Considering one of the provinces, Alberta for example, EEA events increased notably during 2022-2023, with four EEA 2 events and seven EEA 3 events in 2022. The trend continued into 2024 with six EEA-3 events, indicating sustained grid stress during this period.

Figure 2: Frequency of EEA 2 and EEA 3 events in Alberta since 2010

Managing unplanned outages

The reliability of the BPS can be impacted by unplanned outages, which can be caused by extreme weather conditions and create reliability issues if the power system isn’t flexible. Operators need to adjust quickly by redispatching other generators or by using operating reserves. Without adequate resources, the system may struggle to respond to unplanned outages, leading to potential reliability issues. Also, if there are no alternative transmission lines, or if the existing ones are congested, it can be even more challenging.

Recent extreme weather events surfaced these challenges across Canada. For example, in January 2024, Alberta narrowly avoided a rolling blackout during a severe cold weather event that also restricted electricity imports^Footnote 7. With transmission lines from neighboring provinces congested and limited operating reserves available, the Alberta Electricity System Operator (AESO) took measures to maintain power supply, including asking residents to reduce their electricity usage^Footnote 8. Later, in March 2025, a major ice storm left over a million customers without power in Ontario, with some outages lasting over a week due to extensive damage to transmission and distribution infrastructure^Footnote 9. The widespread damage limited available transmission alternatives and overwhelmed system operators’ ability to redispatch resources.

How will future trends affect reliability?

Electricity demand is expected to increase significantly in the coming years^Footnote 10. Trends driving increased demand include electricity’s projected role in decarbonization efforts, with growing electrification of end-uses (like increased electric vehicle use and heat pump adoption).^Footnote 11 Further, new areas of demand growth, like data centers (ex. used to power AI) could also lead to increased growth in electricity demand.

Meeting this rising electricity demand could be a reliability challenge^Footnote 12. Higher electricity consumption could make it difficult for grid operators to reliably provide sufficient power during peak periods.

To meet increased demand while keeping costs and emissions from electricity generation low, additional supply from clean energy sources is widely expected across energy forecasts. Even in scenarios that reflect current policies, many reports project substantial growth in variable renewable energy sources (VRES) like wind and solar, primarily due to their competitive costs.^Footnote 13 Net-zero scenarios naturally show even greater VRES deployment. However, due to their intermittency, VRES must be managed carefully to maintain grid reliability.

Weather conditions also affect consumer electricity demand patterns. During extreme weather events, like heat waves or cold snaps, demand sometimes peaks while VRES output drops, leading to supply shortfalls^Footnote 14. On the other hand, when weather conditions are ideal for VRES generation, output may be high while demand is low, resulting in supply surplus^Footnote 15. This variability poses a challenge for the grid because, unlike conventional generators, solar and wind technologies lack the ability to adjust their output and are not easily dispatchable.

Ways to improve reliability

To ensure a reliable grid, the power system must continuously and safely operate during equipment outages, supply shortfalls, or surpluses. This requires a flexible grid, having the right mix of supply and transmission assets capable of responding to sudden changes in demand or unplanned outages.

One example of how grid reliability can be maintained is supply diversification by integrating VRES with dispatchable technologies such as battery storage and conventional power plants. Battery storage can store excess power during periods of surplus and provide power when needed, while other dispatchable technologies can provide base load capacity to complement VRES^Footnote 16.

Increasing transmission capacity through new transmission lines or non-wire solutions (such as dynamic line rating) can facilitate power transfer from areas with surplus to those experiencing shortfalls. Demand management solutions, like enhanced demand response and the adoption of more energy-efficient devices, can also alleviate grid load.

Widespread grid modernization efforts could help improve reliability. This may include proposing new market structures, integrating new technologies like more accurate forecasting, advanced smart metering, grid automation and Internet of Things (IoT) technology, and energy storage systems^{Footnote 17Footnote 18}.

However, as grid modernization helps improve reliability, new vulnerabilities are also being introduced. These vulnerabilities involve physical and cyber threats and can be seen in smart grids, IoT sensors, and automated systems. To maintain reliability, modernized grids require safeguarding to manage and mitigate these new risks.

Footnotes