round-trip efficiency

Round-Trip Efficiency: Energy Lost When You Store Solar in a Battery

Round-trip efficiency (RTE) is the share of energy you get back out of a battery after charging and discharging. If you store 10kWh and later use 9kWh, RTE is about 90%. Australian households should include those losses when modelling evening savings — especially once Cheaper Home Batteries support (~$372/kWh usable) makes storage mainstream.

CEC-accredited installers only
Vetted and customer-reviewed
Up to 3 free quotes from MrSolar, no obligation
No pushy salespeople

Get Your Free Solar Quotes

Tell us about your home. We'll match you with 3 local installers.

Indicative 2026 pricing: a typical 6.6kW system often quotes around $5,000–$8,000 after the STC discount (metro installs often $5,000–$7,500; premium/regional can run higher). See our solar cost guide.

🔒 No spam. No obligation. 100% free service.

Free for homeowners. Participating installers pay MrSolar a lead fee when matched — that does not buy a higher ranking in our guides or reviews. See how we match quotes and is MrSolar legit?

Where the losses happen

Conversion losses occur in battery chemistry, power electronics and sometimes auxiliary loads. Hybrid inverters add AC/DC stages depending on architecture. Datasheet RTE figures are laboratory values; real homes see seasonal variation.

Why RTE changes bill maths

Exporting at 5c avoids fewer losses than storing for a 35c evening import — even after ~10% RTE loss, storage can win. If your FiT is unusually high and evenings are cheap, RTE losses may argue against cycling as hard.

AC-coupled versus DC-coupled paths

AC-coupled batteries invert twice in some flows; DC-coupled hybrids can be more efficient for PV-to-battery-to-load paths. Ask installers which path your operating mode uses most.

Temperature and partial cycles

Heat and very small cycles can move effective efficiency. A battery in direct afternoon sun on a western wall underperforms a shaded plant room install with the same sticker RTE.

VPPs and efficiency

If a VPP discharges to the grid, you also wear conversion losses for someone else's benefit — offset only by credits. Include RTE when valuing those credits against self-consumption.

Using RTE on quote comparisons

Do not pick a battery on a 1–2% RTE gap alone if usable kWh, warranty and installer quality differ more. Still reject fantasy models that assume 100% free storage. CEC-accredited quotes via MrSolar should show expected daily kWh shifted after losses.

Model storage with real losses — compare CEC-accredited battery quotes on MrSolar.

Related pages

How we verify this page

Written and reviewed by Daniel (Marketplace lead, Epic Unicorn Pty Ltd). We build pages from Australian solar datasets and regulatory references, then map you to CEC-accredited installers only.

Frequently Asked Questions

Many modern lithium home batteries advertise roughly high-80s to ~95% datasheet RTE. Treat mid-90s claims as best-case, not winter reality.
The discount is capacity-based (~$372/kWh usable context), not efficiency-based. Efficiency still changes operating savings.
Calculate the kWh recovered over warranty life. A small RTE gain rarely justifies a large price jump if usable capacity differs.
No — RTE is a storage concept. Panels have conversion efficiency from sunlight to electricity.
Some apps show energy in vs energy out over a month. Divide discharge kWh by charge kWh for a rough household RTE.

Ready to Go Solar? Get 3 Free Quotes Today

Join over 230,000 Australian homeowners who've used MrSolar to find their installer. No obligation, no spam — just competitive quotes from CEC-accredited professionals.

Get My Free Quotes →

Takes 2 minutes. Free forever. CEC-accredited installers only.

Get My Free Quotes →