Two Tesla Powerwalls with 12.28KW Solar

Full Installation Walkthrough

This premium installation features a dual Tesla Powerwall configuration paired with a substantial 12.28KW solar array, representing one of the most comprehensive residential energy systems we have installed. The homeowner was committed to achieving near-complete energy independence and wanted a system that would cover the vast majority of their household consumption, including electric vehicle charging, throughout the year.

The solar array consists of 27 Aiko 455W panels, which are among the highest-efficiency residential panels currently available. Aiko panels use a proprietary ABC cell technology that delivers exceptional output per square metre, making them an excellent choice for installations where maximising generation from the available roof space is a priority. The 27-panel array delivers a combined capacity of 12.285KW, which places this firmly in the large residential category and required a G99 application to Northern Powergrid.

The panels were distributed across two roof faces to make full use of the available space. The primary south-facing roof accommodated eighteen panels in three rows of six, while the remaining nine panels were installed on the east-facing elevation in a three-by-three configuration. This dual-orientation layout extends the generation window across more hours of the day, with the east-facing panels generating strongly in the morning and the south-facing array taking over from mid-morning through the afternoon.

The Solis 8KW inverter was selected to handle the solar generation from both roof orientations. The Solis platform was chosen for its proven reliability, dual MPPT inputs that allow independent optimisation of the two different-facing arrays, and its competitive efficiency rating. The inverter was installed in the garage alongside the two Tesla Powerwall 2 units, creating a dedicated energy hub that keeps all the equipment in one accessible location.

Two Tesla Powerwalls provide a combined 27kWh of usable battery storage, which is an exceptional amount for a residential property. This level of storage means that even on days with limited solar generation, the batteries can store enough cheap overnight electricity to power the property through most of the following day. During summer months, the combination of the 12.28KW array and 27kWh storage creates a system that can go days at a time without importing any electricity from the grid during peak rate periods.

The Tesla Gateway was installed adjacent to the main consumer unit in the hallway, providing whole-home backup capability. With two Powerwalls, the backup capacity is doubled compared to a single Powerwall installation, meaning the property can sustain full operation during extended power outages lasting many hours or even days, particularly if the sun continues to shine and the panels keep generating during the outage.

The installation required careful coordination of multiple trades and technologies. Our roof team installed the 27 Aiko panels across two days, our electricians completed the internal wiring and inverter installation, and the Tesla Certified work was handled by our PW-qualified installers. The consumer unit was upgraded to accommodate the additional circuits required for the solar, battery and Gateway connections, and all existing circuits were migrated to the new board with individual RCBO protection.

Cable management was given particular attention given the amount of equipment and wiring involved. The garage installation features neatly dressed cables in appropriate containment, clearly labelled at every junction and termination point. The two Powerwalls were mounted side by side on the garage wall with symmetrical spacing, and the Solis inverter was positioned centrally above them, creating a visually balanced and professionally finished installation.

The commissioning process involved configuring both Powerwalls through the Tesla app, setting up the Solis inverter through its monitoring platform, and verifying that all systems were communicating correctly and responding to the energy management algorithms. The grid failure test was particularly impressive with two Powerwalls: the 27kWh combined capacity means the property can run on backup for an extended period, providing genuine resilience against prolonged power outages.

The homeowners annual electricity consumption was approximately 10,000kWh including EV charging, and the projected annual solar generation of approximately 10,400kWh means the system is expected to generate more electricity than the property consumes over the course of a year. While there will be a seasonal mismatch with excess generation in summer and a shortfall in winter, the combination of the large solar array and generous battery storage minimises the overall annual grid import to a fraction of what it would be without the system.

This installation represents the pinnacle of what is currently achievable in residential solar and battery storage, and it demonstrates the extraordinary progress the industry has made in enabling homeowners to take control of their energy supply. The combination of high-efficiency Aiko panels, a reliable Solis inverter and the premium Tesla Powerwall storage platform creates a system that will deliver outstanding performance and financial returns for decades to come.