A demand manager, also known as a load controller, is a device that is often installed with a home solar panel system. This device limits the total “demand” a house can use. Demand is the amount of electricity in kilowatts (kW) that the house is using at any given time. This is not to be confused with kilowatt-hours (kWh), which is the measure of how much electricity is used over time.
The more appliances that are run together, the larger the demand is. In the Phoenix, AZ area, the appliance that uses the most demand is the air conditioner. An air conditioner can use between 1 kW and 5 kW in demand, depending how big and efficient it is. Other appliances in the home use demand as well, but typically less than the air conditioner.
The demand manager has a demand limit setting, and the circuits of the large appliances in the home are hooked up to the device. Say, for example, the air conditioner uses just under 4 kW and the demand limit setting is at 4 kW. If someone in the home turns on the electric dryer, the demand manager will cycle the air conditioner off. This is how the demand manager stops the home from going over a certain demand. The device does not stop people from using the large appliances, it just turns off other large appliances to keep the demand low.