We had our first Powerwall 2 installed in November 2022, which provides a storage capacity of 13.5 kWh. The Tesla Gateway, installed alongside, acts as the ‘brains’ of the system, communicating via iOS or Android devices using the Tesla app. The Powerwall is located in our unheated utility area, sheltered from extreme weather conditions. With an average winter ambient temperature of around 12°C, I hope this environment will help extend the battery’s lifespan (I’m only 77 and want to enjoy many more years of use!).

Our 8.1 kWp solar array, consisting of 21 panels, is connected to the Gateway. Each panel has its own Enphase IQ7A micro-inverter. We also have the Enphase Envoy unit, as the solar PV system was installed several months before the Tesla equipment, and we would have had no way to monitor the PV system otherwise.

The Powerwall units feature a sleek white glass front and can be wall- or floor-mounted. They can also be ‘stacked’ one in front of the other, creating a neat installation for the two units that now provide a combined 27 kWh of storage. The Gateway is wall-mounted to the left of the heavy battery and connects to our solar PV system, the grid (after the smart meter), and our consumer unit. We’ve also installed a separate earth rod for grounding when isolated from the grid.

Other articles cover electrical safety and the need for complete isolation from the grid during power outages. Battery owners can continue using stored power or energy from solar PV panels via the Gateway, even charging the Powerwall with solar energy during such times. I won’t delve further into this topic here.

At the time of installation, Powerwalls were as rare as hen’s teeth, and we waited about nine months for delivery of the first unit. We had expressed interest in adding a second unit when installing a heat pump, but our supplier advised waiting to see how the first unit performed. Later, we were told that paying a 25% deposit could secure delivery by February 2024 (15 months later!), but we declined due to the even higher price quoted compared to what we’d paid for the first unit.

When our heat pump was installed in February 2023, the company offered a Powerwall 2 at a significantly lower price, with delivery in just a few weeks. We placed the order, and the second unit was installed in front of the original one – space we had already planned for. This addition increased our storage capacity to 27 kWh, creating a very tidy setup with all control equipment for solar, storage, Wi-Fi, and network links neatly arranged on the same wall.

The Tesla app offers a wide range of options for managing energy use. We can charge the battery at the lowest rates on our tariff, draw energy from the battery or solar PV as needed, and even export energy from the PV and battery to suit our preferences. We also use the NetZero app to complement the Tesla app, allowing us to make subtle adjustments daily. Currently, we’re on Octopus Energy’s Cosy tariff, which provides three low-rate periods throughout the day. This enables us to charge the battery, power our all-electric home, and avoid higher rates entirely.

ROI? Well… if your primary goal is a return on investment, the Tesla Powerwall system might not be for you! We save significantly by using only the cheapest rates on our tariff, and with energy prices so volatile (read: constantly increasing), it’s hard to predict future savings. However, the ability to choose when to use grid power to charge the battery allows us to maximise our tariff benefits while using the greenest energy available.

In short, ROI isn’t the standout feature of a battery installation. While a Tesla Powerwall isn’t a cheap option (and DIY installations using components from various sources can offer significant savings), the system is sleek, reliable and provides a certain ‘smugness’ during storm warnings!

The latest model, the Powerwall 3, offers a few additional features, including a higher current draw from the battery and an integrated Gateway, which should reduce installation time and cost.