Might not fit perfectly with the theme here, but thought people might be interested anyway.

I’d recommend it to anyone who owns their house, has a reasonably accommodating roof (particularly south facing), and plans to be in their house for the next 10 years.

With the 30% US federal tax credit, I expect to make back the investment in roughly 13 years. I’m not counting either the rising price of electricity or the opportunity cost of just putting that money in an index fund.

After 13 years, everything should be profit after that. But it’s not just for the financial reasons.

It’s a 13.7 kw system. Peak I’ve seen it produce so far is around 12.3, with a little less than half the panels facing north. I’m not sure if or when I should expect peak production if not around noon on the summer solstice.

I do recommend having some kind of battery. I went with a Tesla Powerwall 3, partly because I spent so much time haggling and negotiating with my solar installer that I didn’t want to make any further changes. Partly because I expect Tesla to be a name brand that will be around in ten years. Enphase is much better, but it’s also much more expensive. There are probably better options.

I have the Tesla PW3 providing stats through the Fleet API to Home Assistant, which is where these graphics are from. One of the biggest reasons I’d recommend against Tesla is that you’re dependent on your stats to pass through their cloud API and back to you. If your internet goes down, you lose stats. If Tesla gets annoyed with you, or just decides to stop providing the service, you lose stats. If the PW3 still had a local API like the PW2 did, I’d feel much more comfortable with it. I don’t have a home solar installation so that I can be dependent on some company. For anything, if I can help it.

Theoretically, when the power goes out, the PW3 is supposed to switch over in a number of milliseconds low enough to keep all the computers and electronics running. It’s supposed to be an advantage over a generator, which takes a few seconds. The one grid power outage we’ve experienced so far did have a noticeable blinking of lights and a server restart.

The battery allows us to continue to have power when the grid power is out, completely disconnected from the grid. At least in my area, if you don’t have a battery*, your solar goes out when the grid goes down. They don’t want your power feeding back into the grid while they’re working on what should be dead lines. (You can get the cutoff system installed without a battery, but it’s a significant chunk of a battery price, and you might as well just get a battery.)

During the spring, the battery was often lasting through the night. For awhile we tried to be as self-sufficient as we could. My utility company paid us about 10 cents per kWh (in credits only), and charged us about 23 cents per kWh. So early I was trying to minimize use of the grid as much as possible, with automations to use the battery at the early part of the evening and during the morning. Then I realized that, yeah, there’s a difference, but it only settles up once a month. So the ratio is 1:1 until that one day when it settles. Now I’m much less concerned about being self sufficient, though the couple weeks of experimenting with it was fun.

I should have all the hardware, with the Tesla Universal Wall Charger to allow me to use a vehicle as a whole home battery. I just got an Ioniq 6, which I’ve really enjoyed, and has some Vehicle to Load capability. But even though all the hardware is probably there, the software certainly won’t allow anything but a Cybertruck to do the reverse charging through the wall charger. For reference, the PW3 holds 13.5kWh of energy. The car holds 77kWh. So getting that to work someday would basically expand our battery capacity by 6x, and certainly get us through any night where we’re not using AC, likely getting us through multiple cloudy days without AC. (AC uses about 3 kWh per hour, otherwise known as 3 kw.)

Uh, I’ve had this post open way too long, so I’ll just post. I’ve learned quite a bit over the past year. If anyone’s thinking about it or wants to fire off some questions, I’m happy to answer what I can.