Compared to Australia, New Zealand is a mere beginner in the adoption of household solar power – while Australia had 2.68 million installations at the end of 2020 (source: CSIRO), New Zealand had just 33,771 solar installations at the end of July 2021 (source: Electricity Authority).
Like Australia in the early days of its solar rollout, New Zealand is having to create regulatory settings for an emerging market – a notable example being the decisions surrounding metering. And that’s what brought a curious difference between here and Aotearoa: how metering is applied to three-phase household connections where the solar energy is exported on one phase only.
Three-Phase Trickery
Those with long memories might recall an article penned by SolarQuotes founder Finn Peacock for RenewEconomy in 2015, in which he castigated the “three-phase trickery” employed by some utilities. However, it was and remains a claim made by installers that hasn’t been independently verified.
The claim was while most electricity retailers subtracted the household’s exports from the total they were consuming across all three phases, some 3 phase meters were configured to subtract exports from imports only on the phase the solar was connected to.
The difference in electricity bills between the former and the latter configuration can be substantial. Imagine using 3 kW on every phase while simultaneously generating 9 kW of solar power. A three-phase meter in the former configuration would count this as zero net consumption for billing purposes and would cost you nothing. But the latter configuration would bill it as 6 kW of exports and 6 kW of imports. With feed-in tariffs lower than usage tariffs, you are no longer getting free power.
Thankfully in Australia, this misconfiguration of 3-phase meters appears to have ended. But in New Zealand it doesn’t only continue to this day – it’s regulated that way, as was explained to us recently by Dustin Murdock of Red Phase Technology, a two-month-old startup.
At 7c per kWh export and 30c per kWh import, it’s an important issue, Murdock said.
“In NZ, they charge you for exporting at the same time as you’re importing,” he told us.
“So, for New Zealand two- or three-phase customers, if you want your solar to pay off, you want to maximise self-consumption.”
And, of course, because Kiwis can’t rely on their 3-phase meter to net the phases, they want their consumption and production balanced across the phases.
Solving The Problem
Murdock and co-founder Robert Turner have put together a straightforward solution: a device that makes sure loads and solar energy generation are equally distributed across the customer’s two or three phases.
The balancer is yet to be launched, so its name isn’t yet settled.
“That’s where the box of tricks comes in – it pulls power from each phase that has excess generation, and puts it where there’s excess load, so the meter doesn’t see an import”, Murdock said. The box itself is simple power electronics, he added.
“Your solar installer could do it if they were motivated.”
But the extra effort involved doesn’t really fit a business model focused on installing commodity products with increasingly tight margins.
I’d love some data to confirm or contradict this, but it seems there are more multi-phase households in New Zealand as a proportion of customers than in Australia, where the default installation is single-phase.
Murdock told SolarQuotes he believes two- or three-phase households could make up as much as 15% of the total.
“Somewhere between 10% and 20% of people get stuck with this problem.”
And while the NZ solar market is tiny at the moment, it’s likely to grow; making multi-phase metering likely to emerge as a consumer protection issue in the future.
As Murdock told us:
“The solar industry wants the government to change the metering rules, but that’s not working at the moment.”
There is, however, another possible benefit to equalising exports and loads across multiple phases – or will potentially be, when New Zealand reaches higher solar power penetration.
Application In Australia
Australia’s experience is informative here: readers will be familiar with networks attributing voltage rise to excess solar exports, and the resulting regulatory action underway to try and address the issue (Ronald Brakes discussed export limits last December).
If there are a number of two- or three-phase customers on one transformer and their single-phase inverters are all configured to export only on the blue phase, they’ll cause a bigger voltage rise on that phase than if the exports are balanced across phases.
While he hasn’t yet conducted research or marketing covering utilities, Murdock said he can imagine distributors being interested,
“because you can imagine this little device tidying up the loads on distribution networks”.
About Richard Chirgwin
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I wish they just had three phase to one phase inverters, so you could just get your house connected to 3 phase, run single phase on the house side, and go gangbusters
That would mean all your house loads would run THROUGH the inverter and it would have to be rated for your full load, might need to be 20-30kw for most houses for when you have the stove, oven, AV, etc all on. But I get your point, it would make things a lot easier.
Well, at least be able to handle the distribution, so say have two or three separate circuits on the house side, but be able to balance just the grid side.
I just think it’d be technically possible, and then outputting to the grid would not be an issue
That would defeat the purpose of having three phase to run three phase appliances like air conditioners.
In regards to your follow-up, isn’t that exactly what the device in the article does – load balances across the phases. That’s why AEMO is putting the emphasis on end users solving these problems with inverters that will ramp up and down with demand, because it’s not something that was ever needed before in the network so it doesn’t exist at that micro level.
The me the article is referring to some device that switches loads to the most suitable phase.
Michael’s comment was about having a inverter to re-invert the power from a 3 phase input to a single phase output.
I think both are very unlikely to ever happen effectively/very expensive.
So I guess not much tech info has been released yet, but am I reading this right in that this is a device that will actively/dynamically change the phase that loads are on to better load balance across phases?
I don’t see how this could be viable (mostly cost). Surely it would require lots of contactors to switch the loads.
Nice! Very much looking forward to this. I am in NZ with 3 phase solar and am always interested looking at options to increase self consumption. Inverters with unbalanced output are expensive and batteries don’t make financial sense yet. I’m very interested in finding out the pricing and specs when they are available.
Do they have a website?
What a waste. Just fix the stupid metering FFS.
Balancing at a street level is pretty simple and just follows the same rule used to assign which phase a single phase home gets connected to (i.e. it’s based on house numbers, split in such a manner that 1/3rd of homes end up on each phase).
I’m with you, Alex – FFS.
When we got rooftop PV 5 years ago, I thought the ‘right thing’ was to get a 3-phase inverter – to better ‘balance’ feed-in. I initially regretted that decision, as high voltages on 1 phase was causing feed-in clipping. No problem with nett metering though – we were provided with a new smart meter, set up to do this. With enquiries, however, our DNSP made adjustments at our sub-station, and all was good. Now I’m glad for the 3-phase decision – because our existing 3-phase connection is fused at 100 amps/phase – so our voltage rise to the grid is negligable.
We’re on a small farm that has a 2 phase supply. We have 6.6 kW on the roof with a 5 kW Fronius Primo inverter. SP Ausnet limits us to 4 kW export total and per phase, so there’s a Fronius Smart Meter on one phase to control the export. We have no machinery on mains power, so 2 phase is overkill. But, both were in use. You know where this is going, don’t you. I could not reconcile the power bills, even going down to the most detailed level of metering I could access. But I could see pointers to the syndrome described here – it looked like I was being billed for imports on one phase while exporting on the other.
I had my sparky shift the entire house to the same phase that gets the export. Eureka, power bills reconcile, and are considerably lower, especially in summer when we have strong exports.
Sadly, nobody admits responsibility for getting it wrong.
In New Zealand, put simply, when we had solar installed a few years ago we remained on our old meter over Christmas until the electricity company could install the new smart meter. During this period our old meter ran forwards if usage exceeded solar production, and ran backwards when the sun was shining! Use or produce. Credit the same as debit. Now we are paying 36.85c / kWh PLUS GST, and get back just 8c / kWh for what we put back. In what way is this fair?
Hi Drew, I have a 3 phase system and pay Contact 23.8 cents and get 8 cents back for excess generation. Not good but no where near as bad as your 36.85 cents. Daily charge is 98.3 cents.
Hi David, Thanks for that. Time we looked at changing supplier! Although we only pay 33.3 cents daily charge, on anything over 150kWh per month your Contact wins. I’ll check it out. Some suppliers seem to charge more in the far North…? Cheers, Drew
Hi Richard and others, any updates on this? We have just had solar installed on 3 phase, with Goodwe 3 phase inverter and Energizer batter on one phase. Obviously it wont charge from 2/3 of solar from what I’m reading, with that being exported to the grid.
Seems like we are getting ripped off in NZ with our so called smart meters.
Hi Andrew,
Yes you are definitely being ripped off, but not in the way you think you are.
You can’t meter phase to phase connected loads with individual single phase meters – the phase angles make it impossible.
https://en.wikipedia.org/wiki/Blondel%27s_theorem
cheers !