A maximum demand indicator is like a special machine that shows how much electricity a building is using when it is using the most amount of electricity at one time. It works by measuring the electricity that comes into the building and calculating the highest amount of electricity being used during a certain amount of time, like an hour or a day. This helps people who help manage the electricity for the building, like electricians or building managers, understand how much electricity the building needs at its busiest times. This can help them make sure the building has enough electricity and also helps them save money by not using more electricity than they need.