Our Tesla Powerwall gave us a lot more than we banked on

A couple of months ago, my wife and I made the decision to make a more conscious effort to reduce our impact on the environment and hopefully have a long term financial benefit. So to compliment the solar system we already have on our home, we began investigating solar batteries. What a minefield that was but finally we came to the decision on the Tesla Solar Wall 2 and it’s been great. It wasn’t just the reduction in our power use from the grid that made me really happy, the Tesla app helped develop our understanding of power usage throughout the day.

The system: Battery and Control box

Clearly being labelled a solar battery, there’s a big ass battery now bolted to the side of my house. Specifically, the Tesla Powerwall 2 which stores — at full capacity — 13.5kWh of power. The box measures a pretty reasonable 1150mm x 755mm x 155mm and weighs in at 125kg.

There’s also a control box that attaches separately to the battery, as near as is practical to your electrical meter. This is critical to the operation of the system as well as the app because this is where the monitoring is done and data fed through for your app — more on this later.

On paper, the concept is pretty simple but in practical terms, it’s exceedingly complex:

• Solar Power generated goes to the house first, battery second and feeds the grid third
• Let’s say you have a 4kw solar system that is not generating enough power, the battery will supplement your needs if there is a charge, otherwise draw from the grid
• If there’s no solar and no battery, the house draws power completely from the grid

In reality, this is happening in real-time, with constantly changing loads and it’s fascinating to see how much power the house is using at any given time. This can be done thanks to the second control box previously mentioned, that requires Internet connectivity: Hardwired, Wi-Fi and cellular which is all set up as part of the installation.

The App

At a user level, this is where the magic happens because it gives you visibility on your investment. Initially, the impression was somewhat mediocre, but in absolute fairness to the system, there wasn’t great solar production weather for a couple of weeks. My wife described me as a child not allowed to play with a new toy until the sun came!

Our house isn’t massively power-hungry, even with heating running. So the first day with reasonable solar production filled the battery by around 3:30 in the afternoon. That energy reserve saw us through until the solar production resumed in the morning. Our first “off-grid” day felt like a big win, which was then followed by two more days like it.

We were able to track this easily through the app which gives you a lot of data including:

• Your power consumption – by monitoring this, you can also understand what devices use high levels of power.
• Your solar production.
• Your battery use (or charging).
• Your grid power use/feed in.

You can view these as individual metrics, or overlaid graphs to get a clearer picture of your day.

There are a few other great little surprises in the app, starting with the battery reserve. This is a percentage of your battery that you can hold in “reserve” in case of a blackout. We have the default setting of 16% which means that when running on battery, at 16% the battery will go into standby and run from the grid if there is no solar production. Only in the event of a blackout will the reserve power be used. Very handy if you’re reliant upon an alarm clock that resets after blackouts with the risk of you oversleeping for work.

The other that — thankfully — we haven’t used yet either, is Stormwatch. When enabled, your Solarwall will (through the Internet connection) monitor for weather events that are likely to cause power outages. Prior to a predictable outage like this, your battery will fill itself to capacity from the grid in order to maintain your power supply should the likely outage occur.

So far so good…

There’s a lot of very smart decisions that have been made in the manufacture and setup of the Tesla Solarwall 2. Not the least of which is the data collection capacity of the app. Investing in solar storage is a very big decision short term for the financial investment, as well as the longer-term impact on your home and the environmental impact you and your family make.

Right now, if you’re buying a solar battery as a purely financial investment – honestly it’s too early. They’re too expensive and you just don’t get massive gains from it financially. For us, the decision was more based around self-sufficiency with a long term financial benefit. The subsidies offered by the SA Government were, however, the deciding factor with around $9000.00 of a $14,000.00 investment returned over two years. So if you’re considering the investment I highly recommend checking out your local arrangements on renewable energy before throwing too much cash around.

Despite all of that, so far so good. To date, we’re really happy with the investment and once we’re into summer with longer days and better solar production, we’ll have plenty of power to spare. We’ve already learned a lot about our power use patterns and there’s undoubtedly more learning to come across the coming six months.