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Direct Load Control

By Tom Tate

The electric system in the United States can be rightfully classified as one of the engineering marvels of the modern world. Few, if any, other countries can match it for size and performance. Yet, the system is not without its issues and one of the most serious deals with meeting the demand for power on especially hot (or cold) days.

Utilities have a couple of options when it comes to meeting this occasional high demand. They can upsize the lines and equipment to accommodate it safely. Very expensive and not the best use of resources, especially if this expanded capacity is only used a few days a year. They can purchase much more expensive electricity from standby power plants. Hard on the customers’ power bills.

Or, as many electric cooperatives do, they can control when electric loads come on during these peaks.

This direct control of electric load goes by a number of exciting utility-style names including load control, load management and peak demand reduction. The concept behind it is quite simple; your cooperative installs switches on energy consuming devices and when the demand for electricity nears peak capacity, they send a signal over their power lines that turns the switch off. If the equipment is running at the time, it goes off. When the peak passes, they send another signal to turn things back on.

The candidates for such control include electric water heaters and central air conditioning systems. The control strategies differ for each type of equipment. For electric water heaters that have a built in store of hot water, the strategy is to turn them off for a couple of hours or more. Most folks won’t notice because they have a tank full of hot water to use.

Heat pumps and central air conditioning systems are turned off for a few minutes (fifteen is common) then on for fifteen and so forth. In essence, your cooperative takes over the duty cycling of the system so that they can manage peak demand while keeping you comfortable. Even when the compressor is off, the system’s fan will be able to run, circulating cool air until the control cycle passes.

When your cooperative uses a direct load control system, you benefit directly over time with more stable rates. If enough people participate, the total demand for electricity during peak times will drop. Another benefit is reduced “wear and tear” on the grid itself. Even though this sounds odd, serving demand on these hot days pushes the systems towards their maximum capacity. While most of the grid is free of moving parts, it is subject to stress from these loads that weaken equipment and shorten useful life. Replacing this equipment is expensive and increases costs for your cooperative.

Your cooperative may also ask for voluntary conservation on these peak demand days. You can help by moving your thermostat setting up 2 – 3 degrees, postponing energy intensive activities such as washing clothes, drying them and cooking until after the peak, usually until early evening. In other words, generally being careful with electric use when the demand for power is at its height. This not only helps during the peak, it also reduces heat created inside your home during the hottest parts of the day that requires your cooling system to work harder to eliminate.

Throughout this article, there have been numerous mentions of containing costs. Direct load control is all about your cooperative working to reduce costs to you, the member. Conservation combined with load control enables you to directly impact your cooperative’s cost of power.