Solar on 3 phase power - avoiding pitfalls of no net metering

Forums › Home Workshop DIY › Solar on 3 phase power - avoiding pitfalls of no net metering - best inverter?

BossByss

4 posts

Wannabe Geek

#318747 17-Feb-2025 15:35

Kia ora! We're in the process of getting solar. I've received a couple of quotes with some conflicting information, so trying to make sense of it all.

We're rural, work from home with 2 EVs and electric hot water/cooking/heating, so our power requirements are quite high but we're also able to load shift quite well. We're looking at getting a 12 - 14 kW system installed.

We are on 3 phase power, currently set up as 2 phase for the house with the final phase going to the (controlled) hot water.

One of the quotes is for a system with micro-inverters. I think the idea is that the loads would be distributed as evenly as possible across the 2 or 3 phases. However, with the lack of net metering in NZ I think with a system like this avoiding a scenario where you're importing on 1 phase whilst exporting on another seems hard/impossible? And if you add a battery you're somewhat limited in options too? So I think I'm disregarding that option, unless someone here gives me convincing reasons to reconsider ;)

So our best option would be to go for a system with decent panels, and a hybrid 3 phase inverter. If I understand it correctly, a good 3 phase inverter can spread any "unbalanced load" across the 3 phases. Does that eliminate this issue? Would it be smart enough to move excess load from one phase onto another that may need it? The sales people have told me "yes", but then I came across this post: https://www.geekzone.co.nz/forums.asp?topicid=311834 and it appears that in this case the inverter didn't perform as had been promised. I don't want to spend 10s of ks if the system can't provide the financial benefits we'd expect it to....

Amongst the options I've been offered are the DEYE 10kW All-in-One Hybrid Three Phase Inverter, FRONIUS Symo 12kW GEN24 SC Three Phase Hybrid inverter, or the Sigen Energy Controller 10kW Three Phase. Would all of these do the job I'd want it to do for a 3 phase home? And when adding a battery, would all 3 phases be able to "tap" into the battery, or would you pick 1 phase for this (which would then also be the only one that would work during a powercut?).

Many thanks for reading this far, I'd really appreciate any input.

SomeoneSomewhere

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#3343776 17-Feb-2025 16:21

Microinverters can I think sometimes be paired with an AC-coupled battery, but yeah, no ability to shift load between phases without using the battery.

Some inverters explicitly state they can do unbalanced output, and this is usually only some hybrid ones I think. It's not many.

Many three phase hybrid inverters supply three phase backup power. Note that some hybrid inverters are grid-tie only; the battery can be used for load shifting but not as a backup supply.

kiwifidget

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#3343781 17-Feb-2025 16:37

We have 3 phase power and are part way through installing a Powerwall3 solar system from Harrisons.

Their solution is to merge 2 phases into 1 for solar connection, and 1 phase left unconnected to solar.

The only thing on the un-solared phase is the oven.

Delete cookies?! Are you insane?!

BossByss

4 posts

Wannabe Geek

#3344428 18-Feb-2025 23:21

Thanks for your input! I've found the local Harrisons installer to be approachable and experienced with this issue, and we'll likely go for a set up with a Fronius inverter that does "asymmetric feed-in" and should alleviate this issue (there are a few other 3 phase inverters that offer asymmetric generation now, but certainly not all...).

SQLGeek

135 posts

Master Geek
+1 received by user: 32

#3344453 19-Feb-2025 08:51

I've had 3-Phase solar with micro inverters for 10 years, and I certainly do export on 1 phase while import on another, e.g. when the Spa pool is on. It's very inefficient and frustrating.

I looked at the Tesla Power Wall 2 & 3, but would ideally need 3 of them. There's a new 3-phase battery from Sig energy that looks like an ideal solution: https://www.sigenergy.com/en/news/info/1143.html

It's actually better than the Tesla batteries as it's a whole house UPS. I'm a Tesla owner (and share holder), I'd love to go Tesla but this is just better for 3 phase.