Studies have shown that the total energy required to construct a 1000-MW(e) nuclear power plant is about 4.1 × 109 kWh for light-water reactors. This is equivalent to ∼ 1.9% of the total energy produced by the plant (in the form of electricity) over a 30-yr life at an 80% load factor. An additional 3.4 × 108 kWh(e) of energy per year is used in maintaining the fuel cycle for a boiling-water reactor (BWR) and 3.6 × 108 kWh(e)/yr for a pressurized water reactor (PWR). This corresponds to 4.9% of the output electricity for a BWR and 5.2% for a PWR. The total investment in energy is, then, 6.8% for a BWR and 7.1% for a PWR. On a total system energy cost, nuclear plants are comparable to coal plants in that 7.8% of the plant energy is required for deep-mined coal and 6.7% for surface-mined coal.