AC Coupled Grid Tied Battery Backup

[Brames]

Hi Everyone - I am new to the forum but have found the posts extremely helpful as I learn more about the topics here. I currently have a grid tied 7KW PV system and just experienced a nice 48 hour power outage due to a bad storm. I would like to add battery backup to run the bare essentials (well pump, freezer, refrigerator, gas furnace, some lights). I'm calculating I would need ~6kWh for these essentials. I am hoping to do a minimal setup (~1 day of power) now and potentially expand my battery capacity in the future.

I see hybrid/all-in-one split phase AC coupled inverters that can handle the GT PV and batteries but I'm a little confused about what I would need as a minimum battery capacity given my PV set up.

Apologies if this is a trivial question I haven't been able to find a good answer in my searches so far.

 

[sunshine_eggo]

Hi Everyone - I am new to the forum but have found the posts extremely helpful as I learn more about the topics here. I currently have a grid tied 7KW PV system and just experienced a nice 48 hour power outage due to a bad storm. I would like to add battery backup to run the bare essentials (well pump, freezer, refrigerator, gas furnace, some lights). I'm calculating I would need ~6kWh for these essentials. I am hoping to do a minimal setup (~1 day of power) now and potentially expand my battery capacity in the future.

I see hybrid/all-in-one split phase AC coupled inverters that can handle the GT PV and batteries but I'm a little confused about what I would need as a minimum battery capacity given my PV set up.

You must choose an inverter that is capable of AC coupling and can handle the full output of your array, i.e., 7kW or better.

If you've computed that you could survive on 6kWh of essentials per day, then you could get away with only 6kWh of battery; however, you must also factor in the inverter itself as a load.

 

[DIYrich]

What inverter do you have? What is your budget? Any utility incentives relating to battery? Time of use?

 

[Brames]

You must choose an inverter that is capable of AC coupling and can handle the full output of your array, i.e., 7kW or better.

If you've computed that you could survive on 6kWh of essentials per day, then you could get away with only 6kWh of battery; however, you must also factor in the inverter itself as a load.

Yes, that is how I understood everything. I was thinking two, maybe 3, 48V 5.12kWh.

What inverter do you have? What is your budget? Any utility incentives relating to battery? Time of use?

I have microinverters on the roof (2 per panel) for my 7kW system. These bring 240 into the house into a double pole 40A breaker within my GT main service panel.

I am hoping to keep the project $5-10k and do the work myself. I installed my GT solar system myself and everything went well with that project. I'm in Michigan and have consumers energy. I haven't been able to find any existing battery incentives but we do have some bills that may pass soon. At this point I am shooting for 1 day of use assuming no solar generation with the actual use case expecting at least some solar generation during the power outage.

 

[Brames]

I meant two panels per micro inverter ?