Syonyk suggested that I inquire here about this.
I live in Texas. February was an unpleasant wake up call. We experience outages once every couple years, and what’s really upsetting is being unable to make food because the grid is down. Like many others, I decided to add some form of backup power. I had no idea what I needed, so I got some CT clamps and started measuring things. The short answer is: 1.5kW is the peak draw on my critical circuits. More would be great, because not having AC when it’s 110F is not fun, but it’s infrequent enough that it doesn’t make sense to spend a downpayment on a house when I can run fans for a couple of hours.
My initial thought was to buy a generator, but then I stumbled across the SPS feature on the SMA Sunny Boy. The SB can produce up to 2kW on SPS during an outage. And, unlike a generator, the system pays for itself by producing during the 99.9% of the time that the grid is up. However, the rub here is that SPS only produces single-phase/120V. The loads I want to run are in a subpanel fed with both legs from the mains. Either I would need to short the two legs together, which is a terrible idea, or I would need to produce split-phase/240V from SPS. Victron has a 100A auto-transformer selling for $700 on Amazon, but I have not investigated further.
I am weighing this against a second option, which is to put in an off-grid inverter. I would be able to use the full capacity of the array, but I would need to buy batteries, and batteries are expensive and would need to be replaced. I have an existing grid-tied system, and I was told that the off-grid inverter would allow me to use both systems. This seems surprising, so I don’t know if it’s true.
My question is, is there a better way to do this? I’m concerned with value, not cost, which is why solar seems to me a better option than a generator.