[s_tec]

I recently installed an Enphase home backup system as a DIY project (crazy, I know). The biggest problem with any home-backup system is moving the loads onto their own sub-panel. When the utility goes down, power needs to flow into the home, but not to the rest of the neighborhood. To do this, a switch needs to physically disconnect the utility meter from the main loads panel. If this isn't possible (such as when the meter is integrated into the panel), all the loads need to move to a sub-panel. This is the hard part.

Once the meter and main panel are separate, the various backup solutions become pretty similar. The disconnect switch installs between the two, with the solar and battery attached. Sometimes the disconnect switch + solar + battery are all in one unit (like the Bluetti EP900), while sometimes the solar inverter, battery, and switch are all separate units (like Tesla or Enphase). The Tesla switch and battery are sleek & glossy, but the inverters are ugly. The Enphase stuff isn't quite as shiny, but at least the boxes look consistent.

Performance-wise, the systems seem pretty similar as well. Most systems are around $10K for 10KWh of capacity, with somewhere around 6-9 KW of peak discharge rate. I imagine these prices will drop a lot over the next decades. If the battery becomes obsolete, just install a different system. Once the home is correctly wired, swapping the storage system should be pretty straightforward.

[rsync]

"To do this, a switch needs to physically disconnect the utility meter from the main loads panel ... this is the hard part.

It doesn't need to be.

You can just use a physical interlock and toggle between utility breaker and (any input you want) breaker.

You can do this on an integrated meter panel.

This is a dead-simple configuration that you can comprehend - and verify - with your own eyes.

The lock-out switch is NEC compliant, utility approved, etc.:

https://www.amazon.com/Generator-Interlock-Compatible-Homeli...

Yes, you do lose all power for a second or two but ... so much simpler and comprehensible than an ATX solution.

[mindslight]

For a generator, yes.

Is it currently possible to do this with a battery setup, for which its normal state is to feed power to the grid with anti-islanding?

Either you'd need two power connections to the panel - one for the every day anti-islanded backfeed, and then a second with the physical lockout to a different inverter output that operates without the grid.

Or the lockout on the main breaker would need to control a logic-level switch that told the inverter to disable anti-islanding, for power flowing through a separate non-locked-out breaker. This would seem like a better solution, but the inverter/battery manufacturer would have to design for it and get NRTL approval.

[bombcar]

You don't move the loads to the sub panel. You make a new main panel, move the feed to that, and turn the old main panel into a sub panel. Much easier.

[ketzo]

Sort of a silly question -- how do you know that? Where would you recommend I start reading if I wanted to know things like that?

[moffkalast]

Third option: you get a panel of experts and they tell you what to do with the panel.

[newZWhoDis]

You don’t need an isolation switch if you use a sol ark 15k or EG4 18k, you can just tie the grid straight in and they have isolation built in if the grid goes down.

[jaggederest]

This is the way I'm looking to go once I get a few thousand together. They're really impressive hardware and the software is tolerable and updatable.

[rstupek]

Why did you choose the Enphase system versus any of the others? How much capacity did you install and is it upgradeable?

[s_tec]

I like the distributed architecture. Each solar panel has its own inverter, as well as each battery. If I want more panels or batteries, I just add them in parallel with the existing panels or batteries. If a panel or battery goes down, the remaining ones keep working. Avoiding high-voltage DC also makes the project more DIY-friendly. The downside is that Enphase requires users to take online classes before they grant access to the installer app (easy but time-consuming).

Right now I have 3.8KW of solar and a single 3.3KWh battery. We are producing more than we use most months, so the solar is good but the battery is undersized. If we have an extended grid-down scenario like what happened in Texas, the system will mainly provide daytime backup plus a few evening hours. This is still better than nothing, and we can easily add more batteries as we have the budget.

[hedora]

Not the person you asked, but Enphase has a reputation of being much more reliable then the Tesla stuff. You can have up to 40kWh of batteries. I think the peak wattage is also higher per kWh than powerwalls.

Also, we tried to get Tesla to install solar on our roof, and will never do business with them (especially that half of the company) again. There's a reason their solar market share is plummeting. Many news stories have been written on this subject. I won't repeat them here.

LG and Generac also make home batteries. From what I can tell, their offerings are also fine.

The main limitation of all the existing systems (vs. the recently-announced Anker) is that they scale amperage linearly with capacity. This is a pain because the batteries produce way more current than you need, but you have to pay for an electrical bus that can handle peak output. This is why the enphase is limited to 40kWh.

I'd strongly recommend against trying to do the installation of the Enphase yourself. It's extremely hands on.

[cyberax]

If you want something crazier, try doing online backup. So that you don't get any power dropouts.