Round-trip efficiency is the ratio of energy a battery delivers out over a complete charge-and-discharge cycle to the energy put in during charging, expressed as a percentage. At the system level, a modern LiFePO4 installation reaches about 90 percent round-trip efficiency.
Why it matters for home backup power
Every time you charge a battery, some energy is lost as heat inside the cells, the BMS, and the inverter electronics. Round-trip efficiency captures that total loss over one full cycle. A system with 90 percent round-trip efficiency returns 9 kWh for every 10 kWh pushed in. For a solar-charged home battery, that 10 percent loss is the energy your panels must generate above your storage target to actually fill the battery.
One important distinction: runtime and backup-time math uses only the one-way discharge efficiency of the inverter (90 to 95 percent), not the full round-trip figure. The approximately 85 percent usable energy planning figure cited across this glossary combines depth of discharge (80 to 95 percent) with that one-way discharge efficiency; round-trip efficiency is a separate metric applied when calculating charging energy requirements, not when estimating how many hours the battery will run your appliances.(Source: Battery University BU-808)
Round-trip Efficiency in practice
Key numbers
For a Genixgreen LiFePO4 system, system-level round-trip efficiency is about 90 percent, accounting for losses in the cells, BMS and inverter across a full cycle. LiFePO4 cell efficiency alone is typically higher (93 to 98 percent), but real-world system efficiency includes inverter conversion losses and DC wiring resistance. The distinct usable-energy planning figure of about 85 percent of nameplate combines depth of discharge (80 to 95 percent) with one-way inverter discharge efficiency (90 to 95 percent).
Round-trip vs one-way discharge efficiency
Round-trip efficiency measures energy in versus energy out over a complete cycle, end to end. One-way discharge efficiency covers only the output half. Apply round-trip efficiency when sizing a solar array or estimating how much grid or solar energy is needed to charge the battery. Apply one-way discharge efficiency, combined with depth of discharge, when calculating how long the battery will run your home during an outage. Using the round-trip figure in runtime math will understate available backup time.
How Genixgreen uses Round-trip Efficiency
Genixgreen has built LiFePO4 storage in its own factory since 2011 and ships to 100+ countries, with local stock in Odesa for delivery across Ukraine. System-level round-trip efficiency for each product line is validated in factory testing, with the approximately 90 percent figure reflecting full system losses rather than ideal laboratory cell values.
Related terms
- DoD (Depth of Discharge): the share of nameplate capacity used per cycle, which combines with one-way discharge efficiency to set the usable energy planning figure
- кВт·год: the energy unit for both gross and usable capacity, and the base for any efficiency calculation
- Cycle Life: how many full charge-and-discharge cycles a battery completes before capacity falls to 80 percent
- Explore Genixgreen systems with rated efficiency and capacity specifications
- Back to the Energy Storage Glossary
Sources
- Battery University BU-808: How to prolong lithium-based batteries (depth of discharge, usable energy, efficiency in full charge-discharge cycles). https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries