Demand is how much electricity a member requires at a single moment in time. It is measured in kilowatts (kW). Consumption is how much electricity a member uses over a period of time. This is measured in kilowatt-hours (kWh).
Example 1: The important distinction is that demand is an average measure of the rate of electric use, and consumption is a measure of overall electric use.
Assume 10 lights, each using a 100-watt bulb, are turned on. This usage would draw or demand 1,000 watts or 1kW of electricity. If the member leaves the lights on for two hours, that would consume two kWh of electricity.
Now assume five 100-watt lights are used for six hours. Since only half of the lights are being turned on, the demand is cut in half to 0.5 kW. However, since the five lights ran longer, three kWh or more electricity was consumed.
Example 2: The car’s speedometer would be like the demand meter, and the odometer would be like a consumption meter. Compare two cars traveling the same 100-mile road, one car is traveling 10 miles per hour for 10 hours, and the other is traveling 100 miles per hour for one hour. It would take a much more capable and expensive engine to power the car at 100 miles an hour than it does to power the car at 10 miles an hour.