Energy consumption and cost, a comparison with human power 

I summarized the average daily energy consumption perperson and the associated costs in US. All numbers are appropriate to give asense of magnitude. Please correct me if the magnitude is wrong. For ease ofcomparison, all energy units are in kWh, kilowatt hour. To compare with humanmetabolic energy consumption and muscle power output, our metabolic energyconsumption is roughly 100 watts, with a daily consumption of about 2 kWh. Oursustainable muscle power output is less than 100 watts. Assuming a 10 hourworkday, human muscle power out is less than 1 kWh daily.

The prices of natural gas, gasoline and electricity perkWh in Us are roughly 3, 6, and 12 cents. The average daily consumptions perperson are 100, 30 and 10 kWh for natural gas, gasoline and electricityrespectively. From the above numbers, natural gas is the cheapest and mostconsumed energy source while electricity is the most expensive and leastconsumed energy source. This is consistent with our intuition.

Overall, energy is extremely cheap. The total averagedaily energy cost, calculated from the above numbers, is only 6 dollars. The amount ofenergy consumption is higher than 140 human power output. This means we arehiring more than 140 human labours for 6 dollars. In other words, the value ofour daily work, from the energy perspective, worth less than 5 cents. It is theemployment of this extremely cheap energy source that we enjoy our energyintensive lifestyle, such as frequent long distance travels.