Balancing of Electric Supply & Demand

When the demand for electricity nears available supply levels, it’s sometimes necessary to temporarily interrupt the delivery of electricity to maintain the integrity of the electric grid and to prevent catastrophic grid failures and extended outages for customers. This is called shedding load.

Balancing of Electric Supply and Demand

Shedding load may occur if there is a shortage of electricity supply or to help prevent power lines from becoming overloaded. Several factors can lead to load shedding, including extreme weather, sharply increased electric demand, unplanned generation plant outages, transmission constraints, unexpected damage to equipment, unavailability of purchased power or a combination of these situations.

Shedding load is always a last resort, but when necessary this action helps prevent more extensive and prolonged power outages that could severely affect the reliability of the power grid for weeks or even months.


Why is shedding load necessary?

Shedding load is required when the demand for electricity approaches supply, creating the potential for a dangerous imbalance. It’s a way to help reduce power demand by turning power off to some customers for a shorter time to help prevent longer, larger outages. The immediate reduction of power demand is critical to prevent a catastrophic, extended failure of the larger electrical grid.

Power generation and load must always match up or remain balanced – otherwise the grid’s integrity will be compromised. There are strict standards that utilities must follow to maintain this balance.  Shedding load is always a last resort to prevent more extensive and prolonged power outages that could severely affect the reliability of the power grid.

Does this mean all customers are affected if a load shed is required?

Not necessarily. The number of customers affected will depend on the severity of the situation. The more load shed required, the more customers will be impacted. Shedding load is always a last resort, but if needed, it could affect different customers depending on the cause or situation.

Conway Corp’s grid is managed by our reliability coordinator Midcontinent Independent System Operator. A system-wide load shed is initiated only by MISO as a result of an imbalance of supply and demand of electricity and required to protect the bulk electric system – which is interconnected across the country.

Such a scenario could occur due to extreme weather like a hurricane, winter storm or unusually high or low temperatures. Conway Corp has only been required to shed load across our service area once since we entered the MISO market in late 2013, and this load shed occurred during the extreme cold weather brought by Winter Storm Uri in February 2021. Uri impacted much of the country, resulting in record-breaking low temperatures. We have asked customers to voluntarily curtail their electric usage to prevent load shedding, and in most cases voluntary reductions work.

How does load shed work?

Depending on the type of constraint and given impacts to the grid, either Conway Corp or MISO will initiate steps to shed load. For example, if MISO initiates, then Conway Corp must immediately begin shedding load under emergency conditions. This is a requirement to avoid catastrophic grid failures which could result in prolonged power outages.

This could happen at any time of the day or night, and we are given little warning time. It is only done in emergency situations as a last resort, but we must comply to prevent longer, widespread uncontrolled outages.

How do you determine which customers will be affected?

Required outages during a load shed event limit power to some customers who are grouped together. Power in the group’s electricity conductors is turned on and off to their homes or businesses. We typically rotate the temporary outages until the load shed is complete to minimize the burden on any one group of customers.

The groups are determined by the amount of power – or megawatts – that must be shed at the time of the event and can vary greatly depending on the current conditions.

We do our best to avoid critical customers including essential public safety services, health facilities and water systems.

As one group of customers completes its outage cycle, the next group is removed from service and the first is returned to service. In most cases, customers will lose power for approximately 30 minutes.

Why can’t you provide more notice before shedding load?

We provide as much notice as possible to customers in advance of a load shed event. Unfortunately, we are not always afforded time to do that. Load shedding is time critical, and we must comply immediately. We do communicate to customers as soon as possible when we believe there could be conditions leading to load shed.

We are typically provided little notice and must comply with an order from MISO for shedding load to help prevent longer, widespread uncontrolled outages. Click here to learn more about MISO’s emergency messaging and the associated actions their members take.

What exactly is MISO?

MISO is a not-for-profit, member-based organization that ensures reliable, cost-effective delivery of electricity across all or parts of 15 U.S. states and one Canadian province. It is one of the nation’s largest regional transmission organizations. In cooperation with stakeholders, MISO manages approximately 65,000 miles of high-voltage transmission and 200,000 megawatts of power-generating resources across its footprint.

Conway Corp entered the Midcontinent Independent System Operator market in December 2013 and is part of their southern region. Being a part of MISO allows Conway Corp to better coordinate and optimize generation and transmission for the benefit of Conway Corp customers.

Why don’t you just turn off power to industrial customers or turn off street lights to help reduce load demand?

Conway Corp’s load curtailment plan was developed to comply with emergency constraints on generation resources on the transmission grid. Many of our large commercial accounts voluntarily curtail load during these events, but sometimes we are still required to shed additional load.

Voluntary actions by participating business and residential customers serve as a last line of defense before having to interrupt our service. Reduction in curtailable load or calls for conservation could avoid the need to shed load to a broader group of customers. Even if conditions continue to escalate after this step, it still helps reduce the overall quantity of megawatts required to be shed. This means fewer customers are potentially impacted for a shorter amount of time.

Street lights are a very small percentage of our electric demand and do not make up enough of the demand to conserve energy. We cannot remotely turn off street lights so it takes more time and effort than the amount of energy it could potentially save.

What can I do to help prevent a load shed event?

When MISO orders a public appeal for conservation, we immediately ask customers to minimize energy usage as much as possible until the system strain has passed. You can help by:

  • Increasing or decreasing your thermostat, depending on the weather. Even a few degrees can make a big difference.
  • Unplugging electronic devices and turning off lights that are not in use.
  • Holding off on doing chores. Delay laundry, washing dishes and other non-essential uses of electricity.