Although most of the various power sources compared would be impractical or impossible to use in such an application in reality, the purpose of the WSJ graphic is to demonstrate the relative range of energy densities of various common fuels. Several battery-type power sources are also included in the comparison, including lithium-ion, alkaline, and lead acid.
In addition to the three battery types listed above, the power sources compared were diesel fuel, body fat, black coal, propane, natural gas, and wood. The infographic displays the energy density of each of the power sources, and displays the amount of time each could theoretically power an iPhone under several conditions: regular use, browsing, and standby.
The results show that while an iPhone powered by a lithium-ion polymer battery could be expected to last 15 hours under regular use, 10 hours for browsing, and 10 days in standby, diesel fuel – at the top of the list with the highest energy density – would deliver 10 days, 8 days, and 152 days of use, respectively. At the bottom of the list is the lead acid battery, which would only provide one hour of regular or browsing use, and one day of standby.
One fuel source missing from the original list was nuclear. To correct this, Michael Purdie of the Nuclear Energy Institute has provided similar numbers for a uranium power source in a blog post, "I Want a Nuclear Powered iPhone."
According to Purdie, the fission process provided from uranium oxide could power an iPhone for almost 12,000,000 days of regular use – i.e., for over 32,000 years. In standby mode, that time would be extended to 515,000 years.