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.
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.
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.
The National Electrical Code contains the rules for this sort of thing, plus whatever extra rules your local jurisdiction adds. I bought a copy of the code itself plus an "Illustrated Guide to the National Electrical Code" to learn this stuff. There are lots of YouTube videos for electricians, by electricians. DIY channels can also be helpful, but they don't always follow code.
In my case, the local utility requires the electrical meter to be accessible (obviously) and to be a certain distance from the gas meter (obviously). Because of the way my house is shaped, there simply isn't room to move the electrical meter, so a sub-panel was the simplest option. Anything else would involve tearing open the driveway, which would be worse. It really depends on the situation.
It'll give you a really good introduction to house electrical systems, things like "any panel that is connected directly to the utility is the main panel, any panel that is connected to a panel with a shutoff is a sub panel".
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.
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.
Thanks for the info. Do you know how much you saved by doing the install yourself? Did you also do the solar install? I was considering using a battery to time shift power as my power provider has free nights.
I installed the solar first, which cost about $10k for parts, plans, and permits. I got quotes between $18k - $26k for the same-sized system professionally installed, so this was a great savings for 3-4 weekends of physical effort.
I don't know how much I saved on the battery, since I didn't get any quotes. The battery was vastly more time and effort, since I had to move my house onto that backup loads panel.
If you just want to shift usage, the backup panel may not be necessary. The Enphase batteries do support a fully grid-tied mode, where they simply connect to your main panel as a branch circuit. I'm sure other brands do too. This would be an easy DIY weekend project, as opposed to a months-long home re-wiring project. The Enphase mandatory training would be the biggest downside for using them here.
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.
I didn't see much in the way of details on the Anker site regarding their system. It seems none of the companies selling their systems make it as easy as tesla to order one.
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.