Consider a household that uses 23.3 kW-hour of electricity per day on average. (kW-hours is a measure of energy that will be discussed in detail in a later chapter. At this point we want to establish estimations.) Most of that electricity is supplied by fossil fuels. To reduce their carbon footprint, the household wants to install solar panels, which receive on average 320 W/m2 from the Sun each day. If the solar panels are 16.7% efficient (fraction of solar energy converted into useable electrical energy), what area of solar panels is needed to power the household?