Round-trip efficiency (RTE)
How much energy survives a charge-and-discharge cycle.
Round-trip efficiency (RTE) is the ratio of energy discharged to energy charged over a full cycle, including auxiliary loads like HVAC. Modern Li-ion BESS run ~88–92% AC-AC. Every lost point is energy you paid to store but never sold, so RTE decay directly erodes arbitrage margin.
Definition
RTE captures all losses in a charge/discharge round trip: cell internal resistance, power-conversion (PCS) losses, and auxiliary consumption (cooling, controls). AC-AC RTE measured at the point of connection is the figure that matters commercially.
Formula
RTE (%) = (energy discharged ÷ energy charged) × 100
Typical range
New AC-AC RTE: ~88–92% including auxiliaries. A sustained drift below ~85% warrants investigation. DC-DC efficiency is higher but commercially less relevant.
Why it matters
RTE sets the spread you keep on every arbitrage cycle. A 2-point loss across thousands of cycles a year is real money. RTE is also diagnostic: a falling trend usually means rising internal resistance, degraded connections, or auxiliary-load creep.
How NuraVolt tracks it
NuraVolt computes RTE per cycle and trends it, separating cell-resistance-driven decay from auxiliary-load growth, and projects the date it crosses the efficiency floor so the cause is fixed before margin is lost.
Frequently asked questions
See also
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