A higher percentage is not the whole comparison
A proposal showing 95% efficiency can appear better than one showing 90%. But a DC battery-only figure and an AC figure including the inverter are not directly comparable. Establish matching measurement boundaries and conditions first. These percentages are hypothetical, not product specifications or a Kintury Energy assurance.
Sketch the project’s energy path: solar or grid input, equipment before the battery, and the point where output is used. Ask the supplier to mark which part the quoted percentage covers. This reveals losses that a headline figure may exclude.
RTE measures energy returned, not storage capacity
Round-trip efficiency, or RTE, relates energy delivered to charging energy over a defined cycle. The Australian government’s YourHome guide notes that manufacturers may include different components. Conversion and system operation consume energy, so a datasheet figure needs its test boundary.
Do not substitute RTE for usable capacity or state of charge. A battery marked 10 kWh usable does not automatically deliver only 9 kWh at 90% RTE: the 10 kWh boundary and deductions must be known. Counting the same loss twice can also understate output.
A calculation needs explicit assumptions
Suppose 10 kWh enters a defined boundary and 9 kWh returns across that boundary during the completed cycle. RTE is 9 ÷ 10 × 100 = 90%; the difference is 1 kWh. Stored energy at the start and end must be comparable. Otherwise, the difference can include energy still stored rather than losses alone.
To deliver 9 kWh under an assumed constant 90% RTE, the simple input calculation is 9 ÷ 0.90 = 10 kWh, not 9 plus 10%. This is a ratio example only; it does not model charging-power limits, use schedules or changing real-world efficiency.
What belongs in a comparison table
Use one row per model and configuration: RTE, DC or AC boundary, included equipment, temperature, charging and discharging power, tested charge range and document version. Mark undisclosed fields as unconfirmed instead of borrowing another model’s data. Ask whether standby and auxiliary consumption are included.
If the building uses stored energy only on some days, do not automatically multiply full capacity by every day of the year. Build period-specific assumptions from load and available charging surplus. Keep efficiency separate from purchase cost, maintenance, life and backup requirements. RTE alone is not project economics.
When monitored results differ from the specification
Check meter intervals, units, boundaries and starting and ending charge. Do not divide today’s input into output that includes yesterday’s stored energy. Establish whether app figures are estimates or measurements and whether data is missing. Preserve records for the service team rather than opening cabinets or altering circuits to test a percentage.
For discussion with Kintury Energy, prepare the energy diagram, specifications and load profile, and ask which losses the proposal already includes. Request unresolved assumptions and a monitoring approach. Comparable data supports a reasoned choice without guaranteeing savings or backup duration.
