Ideas for covering base load while on-grid?

[j3rk]

I've got both a Tesla solar system on the roof of my house, and a DIY ground-mount system in my backyard, and between the two I cover my pool pump and EV charging during the day, with the excess being sold back to SCE for a few pennies. Outside of solar hours, my base load is about 0.4kWh: freezer, fridge, ceiling fans, etc.). I'd like to be able to cover that base load so I don't pull from the grid unless I need more than that. It seems like I'd only need about 10kWh of battery, but I am having trouble coming up with a solution on how to integrate batteries short of relocating all of my house circuits to a sub panel. I'd like to avoid that, as I just spent $4600 to have my old, maxed out 70's era panel and service upgraded to 200A with some room to grow.

400W doesn't seem like that much in the grand scheme of things. My brain keeps going back to connecting the output of a battery bank to a small, grid-tied inverter wired into the panel to power the whole house when there is no solar coming in. During the day though, I'd want it to somehow be disabled automatically so that the battery could be recharged via an AC charger plugged into the wall to pull from the power already being provided by the two solar systems.

Please tell me this is a stupid idea, and share your better one.

 

[angrygoat]

Couldn't you just use one of those cheap $10 ac timers to disconnect the inverter from the panel during certain time periods? Although, maybe ideally you'd want to disconnect the inverter from the battery, or otherwise turn it off, to prevent idle draw. But the idle draw might be insignificant to your use case.

I think you'd need to do something to prevent back feeding the grid though. I think I read they have special grid tie inverters that constantly adjust their output to ensure you don't feed the grid.

I'm about to do something similar. I have a home on grid power, and my goal is to use a small off grid solar system + battery to 24/7 power a large fraction of my base load (fridge, freezer, office computer) which will get rid of most of my power bill. But I plan to just add new wall outlets next to the current grid power outlets for my fridge and in my office, allowing my to easily choose between grid power and my off grid power if the need ever arises. Solar panels will charge my battery during the day, and I'll probably just use a battery charger on a manual switch to charge at night for days when sun is insufficient. But eventually I'll automate the manual charging part by rigging something to automatically turn the grid charger on at night only if the battery is below a certain threshold.

In my case, it's pretty easy for me to run new wiring to the locations where my big power users are, making this solution really attractive to me. But I suspect that wouldn't be the case for most homes.