Energy and waste in City Life are also considered a kind of income. Energy or waste management that the city provides for itself is cheaper than buying those services externally. Any surplus energy can be sold for profit, as can excess waste management. For example, a power station generates 5100 points of energy. If the city uses only 3100 energy, then the remaining 2000 energy will be sold and is counted as monthly profit. Incidentally this makes the power station one of the best initial industries for a city since it provides work for Blue Collar and profits are much larger than other industrial businesses.