You’re probably not thinking about energy costs, or what drives those costs, when you flip on a light switch or turn on an appliance. Demand, specifically peak demand, is a primary cost driver of electric bills and understanding this concept will help you to become a better informed consumer.
    To help understand demand, here is a quick example.  Electric energy consumption is measured in kilowatt-hours (kWh). Demand is measured in kilowatts (kW). Lightbulbs have varying power ratings, and for this example we’ll use a 100-watt bulb. If that lightbulb stays on for 10 hours, it “consumes” 1,000 watt-hours (or one kWh) but only demands 100 watts. Now, if you turn on ten 100-watt lightbulbs in your home for 1 hour, you are still consuming the same watt-hours (or one kWh). However, you are placing a demand 10 times higher on the utility to have those watts available to you over the course of 1 hour, instead of 10 hours. The demand would be 1,000 watts (or one kW). As more electric loads run simultaneously, your demand for power increases. This requires generators on the electric grid to produce more power to meet your demand. Peak demand is the maximum demand across some period of time.
    It's easy to see why this is an important driver in the cost of providing electric service. The peak demand at your service dictates the size of wire and equipment necessary to serve you and also drives the size of equipment as we aggregate load all the way up to the transmission line and generation resource level.
    Now take a moment to consider how weather affects your use of electricity. Electricity use naturally increases when temperatures reach high or low extremes. Heating and cooling systems run longer and more frequently to maintain comfortable indoor temperatures. Irrigation wells run longer during hot, dry spells to keep up with the needs of crops. During the summer and winter months, when homes and businesses across the country are using more electricity simultaneously, overall demand can approach—or occasionally exceed—available supply. This is especially true during severe weather events, such as winter storms, long hot spells, sudden temperature drops or equipment malfunctions that reduce generation capacity. In rare cases when demand threatens to outpace supply, the regional grid operator may call for temporary, controlled outages—often referred to as rolling blackouts—to prevent broader system failures. If such a situation arises, your power supplier will work to provide timely updates and information to members. 
    To prepare for these scenarios and minimize risks, utilities across the grid— from generation and transmission providers to your local distribution company—work together to implement proactive measures to strengthen reliability year-round. These include routine system maintenance, investments in grid modernization, comprehensive disaster response planning and extensive resource planning processes. These proactive steps are designed to ensure our portion of the grid remains resilient even under extreme conditions. Yet, maintaining a reliable electric system requires a collective effort and every member plays an important role in lowering demand when the grid is under stress.
    Understanding how weather impacts electricity demand is key to maintaining system reliability. By practicing simple energy conservation habits at home, like shifting and staggering your energy use, you may not only save money on your monthly bill, but you will also help increase the resilience of the grid that powers our communities. Together, through small actions and shared awareness, we can ensure that our homes remain warm in the winter, cool in the summer, and that our lights stay on and our local grid continues to serve us reliably throughout severe weather events.