Looking at the Tesla white paper on their inverter, it splits the difference between micro inverters and a single string inverter. It has four separate strings, which may be of different lengths. So it can get a lot of the advantages of micro inverters for, in principle, less money.
The paper is disingenuous about reliability. They spend time comparing prices with micro inverters, but compare reliability with single string inverters. That isn’t a good look.
I don’t buy any claims about advantages in cabling strings over micro inverters. High current DC at fairly high voltages makes me nervous. Much more so than mains. Steel roof, so maybe I should worry more.
Last week we had a pretty severe storm run through. A sizeable branch fell off a tree, and just managed to hit the roof. Only the end hit, so not too much damage. But it punched holes in three panels and smashed up another three. The entire system was still producing power when the electrician who came powered the system down. Enphase micro inverters. Despite Tesla’s claims, which are probably generally reasonable, I would be happy buying Enphase again. The extra money didn’t bother me all that much.
I don’t know about this. Every string inverter does that, and they usually don’t offset the gains from per-panel power optimization…
Honestly, that’s small enough to be a rounding error… I wouldn’t decide based on this alone, one way or the other.
Do you mean you have 4 strings of 3 modules, and another string of five (total of 17 modules)? I guess you essentially end up with five “shading zones” then, but that’s still not as precise as single-module optimization. But either approach might be good enough… this YouTuber explains it from 3:33 to 10:20 or so: https://youtu.be/9GvhDhCSJgo?si=pNfLeu1u5x_vPj1X&t=213
If it’s really just those 5 south-facing modules that are at risk of frequent shading, then you’re talking about a maximum of 30% shading anyway. Bypass diodes will prevent a 100% loss of that entire string. Module-level electronics (microinverters/power optimizers) can squeeze a few more % out of that with certain types of shade, but the difference between the two may not be all that significant.
If you’re really worried about it, just add a few more modules on the roof if you can, to bump the total up to $20k, even if those extra ones aren’t quite optimal.
But I think it would be fine either way…
Personally, I would trust Enphase more than Tesla, but I think that’s mostly because of how much trust I lost in Musk over the last few years. Technologically, from secondhand reports and former colleagues who used to work at Tesla, their tech itself is good, but the company itself really sucks (doesn’t treat its employees well, etc.).
On the other hand, Enphase has built up a lot of hard-won street cred over the years, only does solar, and isn’t a billionaire’s plaything. I’m not saying that to be political, but because ideally home solar is something you’d install and forget about for 20+ years. I would trust Enphase to provide that reliability more than I would Tesla, not necessarily because of any hardware electrical differences, but company cultures and software. (Updates, customer service, warranty, etc… Tesla is notoriously “move fast and break things, fix it later in software”). Between cars, Grok, Twitter, Starlink, solar tiles, Powerwalls, Tesla inverters… I feel like the Tesla brand and Musk are already stretched pretty thin, and I’d be worried about the solar division not being worth their trouble if it becomes a commodity race to the bottom (which it kinda already is). I’d guess they want to shift their deployed fleet (of solar and car batteries) to time-shifting virtual power plants to play energy arbitrage at scale, whereas Enphase just sells devices to installers and resellers.
Shrug. I’d choose Enphase for my own home, but I think the Tesla would probably work fine too. We might be splitting hairs… many people go with microinverters and many go with string inverters, and both companies have their fans and haters. Neither is fly-by-night.
Yes, that is the problem. The differences are symmetrical and trivial. Enphase costs $350 more, and Tesla is estimated to produce 350kWh/year more. There are differences and tradeoffs between the two systems, but they’re minor enough that neither is clearly the winner.
Search of other places isn’t too helpful. The best tell me what I already know. Enphase is definitely the choice if there are shading issues or other complications. Otherwise the comments tend to be the useless “don’t use either, get a XXXX system” or “whichever you get you’ll need to install your own monitoring system.”
Maybe, but that’s just the sales drawing. The final engineering plan may be somewhat different.
Thank you for all of the advice. I have in hand the contract to go with the Tesla inverter, but I haven’t signed it, so I could be annoying and have them change it.