Have you ever wondered what Demand is? Electric demand refers to the maximum amount of electrical power that is being consumed at a given time, as opposed to energy which is the amount of power used over a period of time. For example, a typical hand iron requires, or demand, 1,000 watts of power. If that iron is used for two hours it consumes 2,000 watt-hours of energy.
Using multiple appliances at the same time increases your demand. A typical dishwasher has a demand of 1,200 watts. If you used the dishwasher at the same time as the iron, the total demand for the two appliances would be 2,200 watts. If instead you choose to operate these at separate times, the maximum demand for these two appliances would only be 1,200 watts.