Why I have a Powerwall
The first thing to say is, we (Handled) do not sell Tesla Powerwalls, we provide people with the tools to reduce their power bills.
The reason I have one at home is because we are running an experiment to see if it is worth getting. We like to get practical and actually live through the experience for us to be able to give great advice to our members.
The first step to reduce your energy bill is simply to be on a better energy deal, getting solar or buying battery storage comes after getting the basics set up first.
Should you get a Tesla Powerwall?
If you do all the sums you save about $700 – $800 a year from the battery which costs $12k. That means it will take between 15 – 17 years to pay back the cost. The battery only has a guarantee for 10 years and it is too early to tell what will happen after 10 years has elapsed. Will Tesla swap it our for a new one – ‘trade in’ style? Only time will tell.
The savings come from being able to store excess solar power or energy charged up during “off-peak” times when electricity is cheaper. This stored electricity can then be used at times when it would otherwise be more expensive. Depending on the circumstance the saving per kWh can vary from around 10c/kWh to 50c/kWh. 30c/kWh is a reasonable approximation to be used.
The Tesla Powerwall has a capacity of 13.5kWh. So if you get a full charge and discharge everyday, the maximum amount you’d save would be $1,478 (13.5 x 30c x 365 days). This would mean a minimum payback period of just over 8 years. In my personal experience having had it for just over a year and a half, we have saved $750/yr by having the Powerwall.
The conclusion, my Powerwall will take around 16 years to pay the cost back. So on this basis alone, I would say costs need to come down for it to be worth it.
Does a Powerwall let me go off-grid?
Some Powerwalls, including my own, come with a “Gateway”. The Gateway basically provides energy management and monitoring functions for the Powerwall system, and is the smarts and communications tool for the system. It is controlled by the Tesla App.
When the grid went down, I received a notification from the app that the house was now in back up mode. The screenshot below nicely illustrates the flow of power in my home. It was actually being powered by our solar pv system at the time. The job the Powerwall + Gateway was doing was actually just to ensure that everything stayed on and that the appliances in the home could be safely used.
In working out whether the Powerwall is worth getting, you should consider what having a backup power supply is worth. Let’s say I am prepared to pay $2,000 for this capability, I would then calculate my personal payback as $10,000 / $750/yr = just over 13 years. Probably still a stretch then.
The conclusion for me
I don’t think we’re quite there yet to make this a purely financial decision. For some who either really value having backup power (perhaps you have a lot of outages in your area); or who can replace really expensive consumption with cheaper pricing; this may already be financially viable.
If you are looking to reduce your power bill, this is definitely not the place to start. Start with understanding your energy context and getting on the best tariff for your circumstance. I would then consider getting solar if you have the roof space. Lastly, I would look at getting a battery.
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