Final answer:
The nonrenewable energy source with the highest electricity cost per kWh is likely one with high upfront and decommissioning costs, environmental mitigation expenses, or low conversion efficiencies.
Step-by-step explanation:
The nonrenewable energy source with the highest electricity cost per kWh can vary depending on several factors such as location, technology, and market conditions. Nuclear energy, while having high upfront construction and decommissioning costs, typically offers a lower electricity cost per kWh when these costs are amortized over the plant's lifetime. Fossil fuels like coal and natural gas have historically been cheaper, but environmental regulations and carbon emissions costs can drive their per kWh costs higher. Fusion energy, although not yet commercially viable, may turn out to be very expensive due to the complexity of the technology. Overall, the most expensive nonrenewable energy sources are usually those with high upfront costs, low conversion efficiencies, or high environmental mitigation expenses.
To give an example, if a nuclear plant is built for $10 billion and operates for 50 years with an operating cost of $100 million per year, delivering power at a steady rate of 1 GW, calculating the electricity cost involves amortizing the initial and operating costs over the total energy produced in kWh. The resulting figure can then be compared against the costs of other nonrenewable sources. As a note, solar energy, even though renewable, is not among the cheaper energy resources currently due to high upfront costs, similar to nuclear.