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Electricity Facts
Pumped-Storage and Energy Efficiency—Misconceptions about Pumped-Storage
Every generation project requires energy to run it. All will have an efficiency of less than 100 % (no perpetual motion machines in physics). It takes energy to run the process; we must pedal hard to ride the bicycle uphill. Pumped storage has the highest efficiency when compared to the fossil fuel alternatives.
- Coal-fired plants require energy in the form of coal, usually measured as tons or Btu of coal. A coal plant has an efficiency of approximately 45-55%, meaning that about half of the energy in coal is wasted.
- Natural gas fired plants require energy in the form of natural gas, usually measured as thousands of cubic feet (MSCF) or millions of Btu (MMBtu) of natural gas. Natural gas plants have efficiencies of 70-75%, meaning that 25-30% of the energy in natural gas is wasted.
- Pumped storage plants require energy in the form of purchased electricity, usually measured as Mwh of electricity. Pumped storage plants have efficiencies of over 80%, meaning that only 20% of the energy in purchased electricity is wasted
- The misconception is that pumped storage plants are energy wasters, when in fact they have the highest input energy to output efficiency rating. Since the input is measured in Mwh as is the output, it is easy for a science novice to leap to a false conclusion. The inefficiency of fossil fueled plants is masked by this “units” issue.
- Since pumped storage converts surplus off peak electricity into scarce on-peak electricity, the smaller amount of energy that is wasted is surplus and worth less than the energy that is produced.
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