Energy and natural resources
Round-trip efficiency
The share of energy put into storage that comes back out.
Last reviewedWhat does Round-trip efficiency mean?
Round-trip efficiency is the energy a storage system gives back divided by the energy used to charge it. Some energy is always lost as heat. Lithium-ion batteries typically return around 85 to 90 percent, and pumped hydro storage somewhat less. Example: a battery charged with 100 MWh returns 85 MWh, an efficiency of 85 percent. If it buys power at 20 per MWh in the sunny afternoon and sells at 80 in the evening, each MWh sold effectively cost 20 / 0.85 = about 23.5, leaving a spread of about 56.5 before other costs. Storage profits depend on this price spread, how often the battery cycles, and how fast it wears out.
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