Time-of-Use - Smoothing the Peaks

Reducing peaks in demand takes the strain off the Ontario power system, helps lower the price of electricity and reduces our overall environmental footprint.

Large quantities of electricity can't be stored in a practical way, so it must be produced to meet demand on an instantaneous basis. As a result, the province needs enough generating capacity to meet the highest levels of demand at any one time.

In 2006, for example, Ontario demand surpassed 25,000 megawatts for only 32 hours of the year. As a result, the province needed the extra production capacity - just to meet those few hours when demand reached record levels.

High demand peaks affect the power system in three ways:

• They strain the power system. Particularly during sustained heat-waves, power generators work at almost full capacity.
• High demand pushes up the cost to produce electricity. At peak, more expensive types of electricity production are called upon.
• Peak demand forecasts are used by power system planners to determine how much more power production the province will need in the years ahead. The higher the demand peaks, the more investment will be needed in the electricity system - building new generation plants, new transmission and distribution infrastructure.

Demand Changes Throughout the Day

Electricity consumption goes up and down throughout the day. On weekdays, it starts to rise in the morning as people get up and continues to its peak in the late afternoon or evening as people come home. On weekends and holidays, demand is lower overall.

For the most part, it's the weather that influences how much and when Ontarians consume electricity. Over the last few decades, peaks have become much more pronounced over the summer months as more people install air conditioning in homes and businesses. Peaks in the summer usually take place in the mid- to late-afternoon.

Lighting also affects peak. In the winter, peaks typically occur in the morning, when people wake-up in darkness to begin their day, and in the evening as night falls early.

By conserving or shifting electricity use during peak periods, consumers can take an active role in the management of Ontario's electricity system.

Source: Ontario's Independent Electricity System Operator

Note: If you currently purchase electricity under a contract with a retailer, you will continue to follow the terms and price stated in your contract.