Happy to announce that a few days ago I received my “Permission to operate” from my electrical provider (Eversource in Connecticut).
I was up and running and due to the sunny weather I was able to have a great first day experience – between solar and the powerwall the system covered 42% of my energy usage with less than 8 hours of winter sunshine – this was encouraging!
To be honest though, the next day was miserable weather and production was really low – it is winter after all.
Tesla designed the to be a set-it-and-forget-it install, so it does not require allot of testing and fiddling to run. The only real decision I had to make is the amount of reserve energy I set the powerwall to (see picture below). Some of my testing has shown that with my average winter/Christmas power consumption I can expect the powerwall to be able to run the house for about an hour while using 10% of it’s capacity.
Currently, I have the system set to [Self powered] with a reserve of 40% and [Storm Watch] enabled. With the self powered setting the system will first use solar power to charge the powerwall to it’s reserve capacity and the house is served by grid power. Once the battery is charged to it’s reserve capacity, the system switches to powering the house from solar and only excess electricity over what the house requires is then used to charge the battery to full. If the house needs more than solar can provide the battery will kick in and supply the necessary energy until either solar production can cover the house’s energy needs or it hits it’s reserve capacity setting. The reserve capacity is only used to power the house if there is no grid power.
If the combination of solar and battery cannot cover all the energy that the house is using then the system adds grid power as needed. This is all seamless and unless you look at the app you would not notice it.
What is next?
Now I stop fiddling, let the system run every day and just ignore it. Winter production will be low, I am mainly interested in seeing some electric assistance and having the security of being able to run the house for at least ~4 hours without having to do anything – and longer if I start turning off all kinds of energy using appliances!
[Storm Watch] will make sure that in the event of an upcoming storm the battery will be charged to 100% (using grid power if necessary) and run in back-up only mode for the duration of the storm event. I really like this feature and once I see it kick in (we always have winter storms, it will kick in sooner or later) I will post about it.
Once spring and summer comes around and we have more sun I can start looking at what the system really covers and also see what the actual impact to our electricity bill looks like. With that data we can then make some more decisions regarding our ideas of possibly switching some of our appliances and services to electric. More on that when there is more data to look at.