Export capacity is not the same as PV capacity
A network may allow a rooftop array or inverter that is larger than the amount permitted to flow back to the grid. Static export limits, zero-export requirements and dynamic export controls can all change the useful operating envelope. Before sizing the battery, identify the approved connection terms and whether the limit applies per phase, per connection point or to a controlled inverter setting.
Self-consumption changes the value of daytime generation
Solar used directly by appliances never reaches the export meter. Homes with daytime cooling, water heating, EV charging or business loads can therefore support more useful PV than a low daytime-load home under the same export cap. Build an hourly load picture where possible instead of using annual consumption alone, because two homes with equal yearly kWh can have very different midday demand.
A battery can absorb curtailed energy, but only within limits
Storage can capture some generation that would otherwise be export-limited, but only while the battery has spare capacity and charge power. Once it reaches its reserve or full state of charge, excess solar may still be curtailed. Oversizing a battery solely to avoid occasional clipping can be uneconomic, so compare the frequency and magnitude of export curtailment with other battery uses such as evening load shifting or backup reserve.
Control architecture matters
The inverter, meter and energy-management system need to measure grid flow and enforce the export rule correctly. Multi-inverter or three-phase systems can be more complicated than a single inverter. Check whether the manufacturer supports the required meter, communications topology and dynamic export service in the local market. Do not assume a generic smart meter can provide the control loop.
Model several operating days
Compare a sunny low-load day, a typical day and a high-load day. Include battery reserve, charge/discharge efficiency, EV or heat-pump loads and tariff periods. This exposes whether the design is constrained by export, battery power, battery capacity or household demand and gives a more useful answer than simply matching annual solar generation to annual electricity consumption.
Use the checks together
Battery efficiency guide Battery sizing guide should be used alongside the equipment manuals and local electrical requirements.