Batteries Not Included

 

The breaker panel is that box with the red Caution sign (caution because the solar panel energizes the panel even when the main breaker is off). We are going to get a new larger panel in a week but it will look about the same, just new and taller.

 

So if you’re going to have a spiffy battery system optimizing things, with the ability to power the house when the utility power is off, then you need some kind of smart switch between the meter and the panel. But as you can see, in California there’s no space between the meter and panel, so what to do? Tesla realized the problem a while back and came up with this collar that you put in-between the meter and the wall. Ours is already installed (this was before we got the go ahead from SDG&E to pull a new service):

 

 

 

Other companies have scrambled to implement their own collars (“coming soon!”), but the Tesla is the only one currently approved by SDG&E. There’s other less elegant solutions, but this is what I mean about Tesla targeting the California market.

 

It’s an interesting optimization problem. We will probably switch our service supply plan to “TOU-ELEC” (TOU = Time of Use), which is aimed at customers like us with solar and a battery. TOU-ELEC has the highest difference between on and off peak rates. In the winter this is about $0.30/$0.45 per kWh, but in summer that on peak number goes way up (evening air conditioning). I think we use about 18 kWh per day right now (4-5 kWh is probably the hot tub), and that will probably go up to maybe 25 kWh per day in the winter with the heat pump. The battery allows us to time shift 13.5 kWh. Here is our yearly net usage from the utility (from last June’s annual true-up bill):

So I think the heat pump will bring us back into balance with SDG&E, and those orange bars in the winter should go away. Here is our current solar production

 

 

I’ll be interested to see how the Tesla software handles all the moving parts.