Battery sizing

Start with the load, not the battery brochure

A daily electricity total is only part of the picture. A building with a steady evening load has different storage requirements from a club with a short, high-power lighting demand. PhiSaver provides the circuit and time-of-day measurements needed to make that distinction.

Before choosing equipment, define the objective: using more daytime solar after sunset, reducing a demand peak, or supporting selected loads during an outage. These are different design questions and may lead to different systems.

Measure three things

• Energy to shift: how much electricity the target loads use outside the solar-production window, measured in kWh.
• Power required: how large the load is when it runs, measured in kW, including simultaneous equipment use.
• Charging opportunity: when surplus solar is available, how much there is, and how that changes with weather and season.

PhiSaver’s sports-club case studies identify evening field lighting as a potential battery application. They also show daytime loads that could use solar directly. Reviewing schedules first helps avoid sizing storage around demand that could simply be moved.

Compare realistic scenarios

Use representative measured periods to compare candidate capacities and operating strategies. Include usable capacity, charging and discharging limits, losses, seasonal variation and the applicable electricity tariff. A single sunny day is not a reliable basis for an annual savings claim.

Monitoring supplies evidence for the assessment; it does not by itself establish the final battery design or a guaranteed payback. Backup capability, essential circuits, inverter compatibility and installation requirements need to be confirmed by the system designer and installer.

Check performance after installation

Agree the measurement scope so the relevant battery, solar and grid flows can be checked. Compare actual operation with the intended strategy and investigate unexplained imports, exports or peaks.