Episode 9 – Battery storage – adding a second Tesla PowerWall

2021 – Battery options modelling

In September 2020 we installed our first battery at Sturt Apartments, Christie Walk. You can read the story of our modelling, battery choices and lessons learned in Episode 7 – Battery storage – Tesla PowerWall 2

Everything had gone to plan with the installation of the battery; performance was as expected. The savings generated by our PV upgrade and the battery were flowing into our Green Fund, enabling us to begin planning for the installation of our second battery.

Our modelling indicated that our 21kW PVs were generating enough power to usefully support up to about 55kWh of battery storage, corresponding to 4 x Tesla PowerWall 2 batteries. In cost-benefit terms, a sweet-spot would be with 2 batteries. In the depths of winter in July – on many days – we’d still generate enough spare power to fully charge the batteries for use after sundown.

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Episode 7 – Battery storage – Tesla Powerwall 2

2020 – Battery options modelling

In the middle of all that work on evacuated tubes, we learned that change was imminent in the SA Government Home Battery Scheme. To qualify for the maximum $6k subsidy, applications had to be lodged by 15th April.

Our modelling indicated that our 21kW PVs were generating enough power to usefully support up to about 55kWh of battery storage, corresponding to 4 x Tesla PowerWall 2 batteries. In cost-benefit terms, a sweet-spot would be with 2 batteries. In the depths of winter in July we’d still generate enough net power to fully charge the batteries for use overnight.

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