Which factor is considered in calculating electric bills?

When calculating electric bills, multiple factors are taken into account, making "all of the above" the correct choice.

The square footage of a building is relevant because larger spaces typically require more energy to heat, cool, and power, which can result in higher energy consumption.

The duration of usage is also a critical factor since it reflects how long electricity is drawn from the grid, with longer usage periods leading to increased consumption and thus higher bills.

Energy demand refers to the maximum amount of power used at any single time, which utilities measure to determine the costs associated with supplying that demand, especially during peak usage periods.

When these elements are combined, they give a comprehensive view of how electricity is consumed, allowing utility companies to calculate an accurate bill for the customer based on their specific energy usage patterns.