Engineering True Blackout Resilience: Whole-House Backup vs Critical Load Circuits

When the Western Power grid goes down due to storm activity or network faults, a standard grid-tied solar system automatically shuts off for safety reasons. To maintain power to your property during an outage, your hardware must be engineered with an inverter and battery capable of transitioning instantly into off grid backup mode. However, how long your power lasts and exactly how much of your property continues running normally, depends entirely on the inverter’s flow rate (kW rating) and your battery’s storage size (kWh) .

Think of your battery capacity like a water tank (kWh) and your inverter like the diameter of the hose pipe connected to it (kW). If you have a large 40kWh battery tank but only a standard 5kW inverter pipe, you can only draw water out so fast. If the power draw of your house demands more than 5kW at any one moment, the system instantly chokes and trips off entirely, regardless of how much energy you have stored in reserve.

Sizing for Emergency Grid Down Backup & Extended Performance

Because of that inverter bottleneck, many off-the-shelf battery installations only back up a single, low-draw "critical load" circuit. When an outage hits, you are left sitting in the dark with nothing but a few lights, your Wi-Fi, and the refrigerator running.

That isn't resilience; that is just camping in your own house. At Greener Race, we look at property engineering differently. By deploying high capacity 10kW or 15kW hybrid inverters paired with high-capacity battery storage, we widen that theoretical hose pipe. To put that into real-world outcomes, a 10kW output rating can comfortably run a modern ducted HVAC, house loads still have enough left over to run the air fryer or kettle simultaneously, while a standard 5kW inverter will instantly choke and trip if you try to do the same.

This approach ensures your power outlets, security systems, lighting grids, and primary electronics stay fully active without bypassing your solar and PV system and start importing from the grid or worse still, tripping the internal breaker in the inverter and battery system.

But everyday resilience isn't just about blackouts—it's about surviving the daily Western Australian pricing structure. For homes on the Synergy Midday Saver tariff, your battery must also act as a shield against the punishing 3:00 PM to 9:00 PM "Super Peak" window, where grid electricity costs explode to over 55c/kWh. If your inverter isn't sized to run your entire house off the battery during this afternoon Danger Zone, you will be forced to buy that expensive grid power every single day.

While each property is different our General recommendation are 10kW (1 phase) or 15kW (3 phase) inverter capacity depending on your power supply as these are the standard approved by Western Power. For battery storage for most situations 25-35kWh, or 40+ kWh of battery storage capacity for large or heavy demand properties.

Load Balancing: Why we recommend heavy loads to be separated

Even with a high-capacity 15kW inverter handling the load, energy management during a blackout requires some discipline. While the system possesses the capacity to power heavy appliances, running heavy loads like ducted air conditioning or EV chargers will drain your tank quickly. For context, running a standard 14-16Kw cooling/heating ducted air conditioning will use around 5Kw of electrical power and completely drain a fully charged 15 kWh home battery in around 3 hours, before taking into consideration the other loads like back up lights, fridges and general power.

Because of this rapid drain, our standard practice is to isolate heavy electrical loads from the essential backup supply circuit. If a blackout hits the grid while you are away from home, the last thing you want is for your automated climate control system or your EV charger to suck your entire battery reserve dry before you even get home. By separating these heavy loads, we ensure your essential refrigeration, security, and lighting can coast for days, not hours. This doesn't mean your solar and battery doesn't power them, it just means when the grid is active these heavy loads not able to draw from your backup power or be used.

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