# Round-Trip Efficiency

The proportion of energy put into a battery system that comes back out again, after accounting for losses in charging, storage and discharging. A round-trip efficiency of 90% means ten kilowatt-hours in returns nine.

Source: https://inverterdata.com/en/glossary/round-trip-efficiency/
Site: InverterData (inverterdata.com) — open technical specification database
Last updated: 2026-08-24
License: free to quote with attribution to inverterdata.com

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Compare figures carefully, because manufacturers measure round trip at different boundaries. A DC-to-DC figure covers only the cells and is flattering; an AC-to-AC figure includes the inverter's conversion losses in both directions and is what a household actually experiences. Standby consumption also matters: a system that idles at tens of watts around the clock quietly erodes the benefit of a small battery. Losses appear as heat, so poor round-trip efficiency and a hot-running installation tend to travel together, and both worsen at high charge and discharge rates.