Home battery backup usage case discussion

[EbS-P]

I want to discus the best way to use my new whole house battery backup. It’s a Tesla power wall 3 with 13,5 kWh of storage. Net metering makes these really a standby power system when the grid goes down. Its default is to charge from solar but it will charge from the grid but I’m not sure if I can force that.

I can set the minimum state state of charge under normal grid up conditions. Right now I just picked 70%. That means in the evening once the PVs are not producing enough the battery will discharge all the way down to my set 70% before using grid power.

With net metering this is rather pointless to save me money. I get net metered then sell my overage back at $0.03/kwh. What I don’t know is if my surplus carries over month to month or the pay out at the end of the month and I start each month with now surplus. (I should have asked but didn’t really care what the answer was because it’s not like has a choice in utility providers and I don’t think the extra incentive money is going to be around for ever).

So the question is if the battery has a 10 year warranty (70% capacity at 10 years with unlimited cycles. And another warranty use case 70% at 10 years and 38 Mwh throughput. That works out to be 280 full cycles per year for 10 years ) where should I set my discharge limit. Really low meaning the battery will have more cycles or at 100% meaning the battery is only used for backup power? How much greener is using more of the battery on a daily basis. Is storing my solar electricity and using a full batteries worth of electricity each day any greener than just sending my excess generation to the grid.

here is a pretty graph showing the battery usage in green, solar in orange and grid in grey.

 

[stoveliker]

I don't know.

Though it depends on what your grid has. If you're offsetting coal by sending it to the grid, it's good.
If you're offsetting hydro, put it in your battery and use more yourself to avoid needless transport of power (=losses!)

But some utilities have a once a year kWh bank reset, i.e. the accounting happens once a year.
If that is the case for you too, normally that would be one year from when you started. But you want to reset that to the first month in the year that your usage breaks even after the winter.