The short version
Key points
- The installation took three working days spread across nearly eight days because rain delayed roof work.
- The system includes 25kWh of nominal battery capacity in five 5kWh modules, with approximately 20kWh considered practically usable after system limits and reserve.
- The solar installation was expanded from approximately 6.6kW to around 13.2kW, and the inverter was upgraded from 5kW to 10kW.
- Over 23 days, the system imported 33.4kWh from the grid and exported 115kWh.
- Pat estimates the system could save about $140 per month before accounting for the financed portion, or about $90 per month after that calculation.
What was installed
The completed system uses Growatt’s APX S2 battery system, with five 5kWh modules providing 25kWh of nominal storage. Pat explains that the system reports about 22.5kWh as usable, while a further 10% reserve is kept from discharge. He therefore rounds the practical usable capacity to approximately 20kWh.
The installation also added roughly 6.6kW of solar to an existing 6.6kW array, bringing the total to approximately 13.2kW. The inverter was changed from 5kW to 10kW. The system includes separate battery, controller, inverter and backup components, as well as a backup module, which creates a larger and more visibly complex installation in the garage.
Installation experience and backup setup
The installation took three working days, although those days were spread over nearly eight days. Rain stopped the team from completing the work on the planned second day, particularly because roof work was required for the additional panels. Pat says the installer attended to his requests, including positioning the equipment away from cars, adding bollards and disconnecting his Tesla charger from the solar and battery system.
The home has three-phase power, but the Growatt backup arrangement is single-phase rather than three-phase. Pat says most of the house will remain powered during an outage, except for the air conditioning. The home uses gas for cooking and hot water, which reduces the backup load. He also reports that the installer configured the inverter to provide up to 10kW per phase, but notes that he has not found documentation confirming this arrangement.
Features and limitations
Pat chose Growatt partly because a previous Growatt inverter had worked well and because the brand was positioned as a more affordable option. He also valued the local support provided by Sunterra, which he says has operated in Western Australia for nearly 16 years. The modular design means individual components can potentially be replaced separately rather than replacing a combined unit.
The Growatt app is described as average, while the web interface is preferred. The system also integrates with Home Assistant, which Pat uses to estimate how many hours of battery capacity remain overnight. Limitations include the lack of three-phase backup, a requirement for an internet connection to maintain the warranty, and no integration with third-party chargers such as the Tesla charger. Pat says the system can export a maximum of 1.5kW to the grid.
Performance after 23 days
During the first 23 days, the system exported 115kWh to the grid. Pat says the battery was at 100% going into the night on 98% of those days, with one day reaching only about 40% because of persistent rain.
The home imported 33.4kWh from the grid during the period. These imports mainly occurred between approximately 5:30am and 6:30am, when heating the house used enough energy to reach the battery’s 10% discharge limit before the sun came up. The electric vehicle was excluded from these figures because its charger remains disconnected from the solar and battery system.
Using the household’s electricity consumption and an EV time-of-use tariff, Pat calculated $7.91 in grid energy costs over the 23 days. He estimates this could be around $10 per month for the early-morning top-ups, although the figures are based on a short period that included rainy weather.
Cost and estimated payback
The total system cost was $15,930. Pat uses a recent $696.12 electricity bill as a starting point, but rounds the comparable bill to $660 and removes the connection charge. He then estimates the household’s non-EV energy cost at $240 per month, subtracts approximately $10 for battery top-ups and allows $90 per month for the financed portion of the system.
On that basis, Pat estimates the system leaves him about $90 better off each month after the financing calculation. For the battery and installation cost as a whole, he calculates a simple payback period of about 70 months, or approximately six years. He stresses that this does not account for future electricity price increases and that the figures are an early estimate rather than a complete long-term result.
TechManPat’s conclusion
I’m absolutely stoked with the system so far. After 23 days, it has largely covered the household’s overnight use and reduced grid energy costs to a small amount, although the next electricity bill will provide a more meaningful comparison. My current estimate is a payback period of around six years, but the result will depend on future usage, energy prices, battery performance and the final billing data.
This knowledge-centre summary is based on the linked TechManPat video and reflects the information available when it was published. Check current pricing, availability and policies before acting.
