Image is a graph from the electric company showing my usage for a day this week. From 6:30 AM to 8:30 PM we used absolutely no utility power.
I’m almost at the three week mark for having this system up and running. The first two weeks I only had 3 KW of PV input but I added another 5 panels to bring it up to 4 KW last week. It’s also still running from a transfer switch in “off grid” mode because I don’t yet have the prep work done to move my breaker box and start moving circuits to it. (That means I’m either on full solar+battery or utility, no mixing or load sharing).
Once I get it wired in fully, I’m probably going to switch to time-of-use billing. Unfortunately, I can’t do that ahead of time because rather than just making off-peak use cheaper, it makes peak usage (M-F 7am to 9pm) extremely expensive while off peak dirt cheap. I wish there was a middle option, but it is what it is.
I’m also being very conservative with my battery usage since I want to have at least 50% in “reserve” to cover power outages. That’s especially important during these heat waves. We could easily run 24/7 but would have to take a day off every so often to just let it charge back up since my system is a bit too small to cover all our usage indefinitely (at least if we want to run the A/C for comfort, that is).
We do lose power during the switchover. Same as if a backup generator were kicking in (a backup generator is pretty analogous to how I have this wired up currently)
My WFH office, homelab servers, 3D printer, and the fridge are all on UPSs. Fridge is a long story, but a UPS has proven beneficial to deal with its Samsung-ness. Everything else doesn’t really care since it’s only a literal split second to make the switch.
The only drawback to this manual switchover is the oven and microwave clocks are never right. But to be honest, even before we started switching over to solar every day, the power would flash almost as soon as we set them so we largely just ignore them. Side effect now is they’re both timers showing how long we’ve been on solar that day.
Once I get it installed fully, there will be no cutover. It acts as an on-line UPS, essentially, and the only thing that changes is where the inverter is drawing it’s power (PV, battery, utility, or a combo of any of those). It also, supposedly, has a 10ms switchover time if it has to go into “bypass” mode to feed the load directly from utility input. 10ms is comparable if not the same as the switchover time on my other UPSs.