In atmospheric chemistry, a parameter called residence time is defined for each gas as inline-formula
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, where inline-formulaM represents the mass of the gas in the atmosphere and inline-formulaF is the total average influx or outflux, which in time averages are equal. In this brief communication, we extend this concept from matter to energy which is also a conservative quantity and estimate the average residence time of energy in the atmosphere, which amounts to about 58 d. A similar estimation for the residence time of energy in the Sun is of the order of inline-formula107 years, which agrees with the Kelvin–Helmholtz timescale.