Round-Trip Efficiency — the fraction of energy recovered after a full charge-discharge cycle. LFP batteries typically achieve 85–92%. Where NEMPulse shows a per-unit RTE it's measured from AEMO's own data, not assumed — a dash means the fit didn't clear acceptance checks, and the model falls back to ~86%.
Round-Trip Efficiency (RTE) is the fraction of energy a battery gets back out after putting energy in through a full charge-and-discharge cycle. If a unit draws 100 MWh to charge and can then discharge 88 MWh, its round-trip efficiency is 88%. The lost energy is dissipated as heat in the inverter and the battery chemistry itself; lithium iron phosphate (LFP) systems, which dominate new NEM builds, typically achieve 85–92%.
RTE matters for economics because it sets a floor on the price spread a battery needs to arbitrage profitably: at 85% efficiency, a unit must sell for at least ~1.18 times what it paid just to break even on the energy round trip, before any other cost. It also matters for NEMPulse's data: where AEMO has not yet published a unit's reported state of charge, NEMPulse integrates SOC from dispatch MW using that unit's round-trip efficiency, shown as a dotted line to mark it as inferred rather than measured.
Since AEMO publishes each unit's reported energy storage (INITIAL_ENERGY_STORAGE), NEMPulse measures round-trip efficiency per unit rather than assuming a fleet figure. It regresses the reported storage change on the energy actually dispatched at the connection point, over steady (non-ramping, non-regulation) 5-minute intervals in a trailing 30-day window, refreshed weekly — so the figure captures inverter, transformer and auxiliary losses for that specific site, and moves as the asset ages. A measurement is only published where it clears acceptance checks: enough steady charging and discharging intervals spread over several days, a round trip inside a physically credible range, and a tight fit. Units that do not clear them show a dash and fall back to the ~86% (0.9275 × 0.9275) modelling assumption internally; hybrid units are excluded outright, since solar charging the battery on the DC side looks identical to impossibly good charge efficiency.
Treat the published figure as a measurement of each unit rather than a league table. AEMO does not publish where a unit meters the energy it reports as stored: a unit measuring at its connection point yields a true AC-to-AC round trip, while one measuring on the inverter's DC side leaves transformer losses out and reads a few points higher. Fits above 95% are therefore withheld, on the basis that an AC round trip above roughly 94% is not credible for grid-scale storage once inverter and transformer losses are counted. Two smaller effects also flatter the number: it is fitted on steady, mid-power intervals, which is where an inverter is most efficient, and it excludes the site's standby draw.
Related terms: SOCEnergy Arbitrage
See also: Battery detail pages
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