What is Round-Trip Efficiency?
The percentage of energy you get back out of a battery compared with what you put in to charge it.
Quick Answer
Round-trip efficiency matters for UK solar economics: the higher it is, the more of your cheap or free solar energy you keep when shifting it to the evening peak. Most popular UK home batteries quote 90 percent or more. Compare it alongside usable capacity and warranty when choosing.
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
Round-Trip Efficiency Explained
Round-trip efficiency measures how much energy a battery returns compared with the energy used to charge it. If you store 10 kWh and can later draw 9 kWh, the round-trip efficiency is 90 percent, with the rest lost as heat during charging, conversion and discharging. Modern lithium iron phosphate (LFP) home batteries typically achieve 90 to 95 percent. Higher round-trip efficiency means more of your stored solar energy is actually usable.
How Does Round-Trip Efficiency Work in the UK?
Round-trip efficiency matters for UK solar economics: the higher it is, the more of your cheap or free solar energy you keep when shifting it to the evening peak. Most popular UK home batteries quote 90 percent or more. Compare it alongside usable capacity and warranty when choosing.
Frequently Asked Questions
What is a good round-trip efficiency for a solar battery?
90 percent or higher is good for a home battery. Modern lithium iron phosphate (LFP) batteries typically reach 90 to 95 percent, meaning you get back 90 to 95 percent of the energy you used to charge them, with the rest lost as heat.
Why is round-trip efficiency important?
It determines how much of your stored solar energy you can actually use. A higher round-trip efficiency means less is lost when charging and discharging, so more of your cheap daytime solar is available to offset expensive evening grid electricity.
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John Rooney is the founder of Solar Info and has been covering the UK solar energy market since 2023. He researches every battery and inverter brand against manufacturer datasheets, MCS and Ofgem data, and feedback from the MCS-certified installers in our directory before publishing.