Solar options for home in 2022

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13 posts

Geek

#3462197 17-Feb-2026 12:50

Yes, payback is long at current prices, which a better time based FIT would help.

Power during outages is helpful to keep my HA and web and mail systems up, as we had a unplanned long one recently.

Panel was sized to fill up the optimal roof space now.

With a TOU plan, the goal is to use the night rate to charge the battery.

This should cover any daytime winter cost and have surplus to sell in summer.

Already planning on moving to electric water heating, given the rising gas cost and will do it if the califont dies.

Still looking for a good night rate deal, as our current rates (inc GST) are: Anytime low user, Daily $1.38, kWh $0.3381

I did think of going for a smaller HV battery capable system and scrapping the leaf for it's battery in a few years. It will probably still do 8kWh by then.

Paul1977

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#3462198 17-Feb-2026 12:52

Can someone shed some light on something for me:

I've been quoted some rates from PowerEdge and they quote their Export rate as 17.39c (20c incl GST). But they don't mention GST on their import rates. See below for one of the options presented:

Fixed daily fee: 285c per day (fixed for 2 years)
All Day Import rate: 21.4c per kWh (fixed for 2 years)
Export rate: 17.39c per kWh (20c incl GST) (fixed for 2 years)
Electricity Authority Levy: 0.15c (or $0.0015) per import kWh

So, as residential user, what does that actually mean for me? Would I be getting 20c for my exports, and paying 21.4c for my imports? So a differential of 1.4C?

HarmLessSolutions

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#3462203 17-Feb-2026 12:56

Paul1977:

Can someone shed some light on something for me:

I've been quoted some rates from PowerEdge and they quote their Export rate as 17.39c (20c incl GST). But they don't mention GST on their import rates. See below for one of the options presented:

Fixed daily fee: 285c per day (fixed for 2 years)
All Day Import rate: 21.4c per kWh (fixed for 2 years)
Export rate: 17.39c per kWh (20c incl GST) (fixed for 2 years)
Electricity Authority Levy: 0.15c (or $0.0015) per import kWh
So, as residential user, what does that actually mean for me? Would I be getting 20c for my exports, and paying 21.4c for my imports? So a differential of 1.4C?

I question Roy on the import rate GST thing before realising this stated in his original email.

"We are delighted to present our rates tailored for low-power user ICP 000XXXXXXXX (excluding GST):"

https://www.harmlesssolutions.co.nz/

HarmLessSolutions

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#3462206 17-Feb-2026 13:00

mark0x01:

Yes, payback is long at current prices, which a better time based FIT would help.

Power during outages is helpful to keep my HA and web and mail systems up, as we had a unplanned long one recently.

.....

Higher FIT is a double edged sword. The greater the value of your export the less the differential between import and export which is where your battery ROI lies. For a non-battery system <8 years payback is to be expected.

https://www.harmlesssolutions.co.nz/

Paul1977

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#3462212 17-Feb-2026 13:13

HarmLessSolutions:

I question Roy on the import rate GST thing before realising this stated in his original email.

"We are delighted to present our rates tailored for low-power user ICP 000XXXXXXXX (excluding GST):"

Oh right, so all exclusive of GST? So for me the actual import rate would be 24.61c? So a differential of 4.61c?

That wasn't entirely obvious. Still pretty good, but not as amazing as I thought it might have been!

I'll compare this with my usage patterns and solar generation estimates to their day/night plan (slightly higher day import, but much lower night import). These are the "Standard User" prices (hence the high daily fee) as, even with solar, I estimate our grid usage over the entire year to exceed the threshold for the "low user" plans to make sense.

EgorNZ

64 posts

Master Geek
+1 received by user: 23

#3462240 17-Feb-2026 14:16

Couple of points that seem to always get lost about batteries when people are making back-of-an-envelope ROI calculations:

You can charge the battery from the grid, not just from solar generation. If you're on a time-of-use plan with a big differential in pricing this can offer much better arbitrage opportunities than only comparing import/export. And this is possible every day regardless of season or weather conditions.
You're (currently) limited to 5kW export which can result in significant generation capacity being wasted on sunny days if you have a larger solar array. A battery can help soak this up.

Regarding GST, you will be paying GST on imported energy but can only collect GST on exported energy if you are GST registered, which very few households are. So most people want to compare (import price including GST) vs (export price excluding GST).

mark0x01

13 posts

Geek

#3462263 17-Feb-2026 15:33

EgorNZ:

Couple of points that seem to always get lost about batteries when people are making back-of-an-envelope ROI calculations:

You can charge the battery from the grid, not just from solar generation. If you're on a time-of-use plan with a big differential in pricing this can offer much better arbitrage opportunities than only comparing import/export. And this is possible every day regardless of season or weather conditions.
You're (currently) limited to 5kW export which can result in significant generation capacity being wasted on sunny days if you have a larger solar array. A battery can help soak this up.

Regarding GST, you will be paying GST on imported energy but can only collect GST on exported energy if you are GST registered, which very few households are. So most people want to compare (import price including GST) vs (export price excluding GST).

mark0x01

13 posts

Geek

#3462265 17-Feb-2026 15:41

mark0x01:

EgorNZ:

Couple of points that seem to always get lost about batteries when people are making back-of-an-envelope ROI calculations:

You can charge the battery from the grid, not just from solar generation. If you're on a time-of-use plan with a big differential in pricing this can offer much better arbitrage opportunities than only comparing import/export. And this is possible every day regardless of season or weather conditions.
You're (currently) limited to 5kW export which can result in significant generation capacity being wasted on sunny days if you have a larger solar array. A battery can help soak this up.

Regarding GST, you will be paying GST on imported energy but can only collect GST on exported energy if you are GST registered, which very few households are. So most people want to compare (import price including GST) vs (export price excluding GST).

Yes, charge from grid is a bust with Electric Kiwi Movemaster, overnight rate at 0.2888c and best export is peak time @0.23c, so just losing money there.

MainPower now approves up to 10kW for single phase installations, so not an issue here.

GST is a bummer too. At least we don't pay tax on exports (yet).

Doesn't look too rosy the deeper I look.

Paul1977

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#3462266 17-Feb-2026 15:42

EgorNZ:

Couple of points that seem to always get lost about batteries when people are making back-of-an-envelope ROI calculations:

You can charge the battery from the grid, not just from solar generation. If you're on a time-of-use plan with a big differential in pricing this can offer much better arbitrage opportunities than only comparing import/export. And this is possible every day regardless of season or weather conditions.
You're (currently) limited to 5kW export which can result in significant generation capacity being wasted on sunny days if you have a larger solar array. A battery can help soak this up.

Regarding GST, you will be paying GST on imported energy but can only collect GST on exported energy if you are GST registered, which very few households are. So most people want to compare (import price including GST) vs (export price excluding GST).

Ah, that changes the calculations a little.

EgorNZ

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#3462267 17-Feb-2026 15:43

mark0x01:

Yes, charge from grid is a bust with Electric Kiwi Movemaster, overnight rate at 0.2888c and best export is peak time @0.23c, so just losing money there.

Of course one has to choose an appropriate plan to take advantage of this.

Paul1977

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#3462271 17-Feb-2026 16:02

mark0x01:

Yes, charge from grid is a bust with Electric Kiwi Movemaster, overnight rate at 0.2888c and best export is peak time @0.23c, so just losing money there.

MainPower now approves up to 10kW for single phase installations, so not an issue here.

GST is a bummer too. At least we don't pay tax on exports (yet).

Doesn't look too rosy the deeper I look.

Plus if they only give the 23c export during peak (which they define as weekdays 7am-9am & 5pm-9pm), then it's essentially meaningless isn't it? How much solar generation will be happening then? It's only11.5c export when you will actually be generating. They have a low daily fee, but their peak import rate is very high @$0.5927 where I live.

PowerEdge is looking like it might be best for me. Very high daily fee, but for my usage still looks like the best value.

mark0x01

13 posts

Geek

#3462273 17-Feb-2026 16:10

Paul1977:

mark0x01:

Yes, charge from grid is a bust with Electric Kiwi Movemaster, overnight rate at 0.2888c and best export is peak time @0.23c, so just losing money there.

MainPower now approves up to 10kW for single phase installations, so not an issue here.

GST is a bummer too. At least we don't pay tax on exports (yet).

Doesn't look too rosy the deeper I look.

Plus if they only give the 23c export during peak (which they define as weekdays 7am-9am & 5pm-9pm), then it's essentially meaningless isn't it? How much solar generation will be happening then? It's only11.5c export when you will actually be generating. They have a low daily fee, but their peak import rate is very high @$0.5927 where I live.

PowerEdge is looking like it might be best for me. Very high daily fee, but for my usage still looks like the best value.

Looks like they have all done the caculations so they get the most benefit from our solar.

fastbike

448 posts

Ultimate Geek
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#3462277 17-Feb-2026 16:54

Paul1977:

Not sure your reasoning for not touching Telsa. But doing the numbers the ROI on a battery just doesn't add up for us. It looks OK when the supplier punches the figures into their ROI tools, but that doesn't paint the full picture. The figures below are based on the best rates I could find and our specific power usage patterns.

It looks like 24 Aiko 480W panels and 10kW Fronius inverter with no battery could reduce our yearly power bills by $2,500 from an install cost of around $22,000 giving an ROI of 8.8 years ($22,000/$2,500).

Change to 24 Aiko 480W panels and Powerwall 3 (13.5kW battery with built-in 10kW inverter) could reduce our yearly power bills by $3,000 from an install cost of around $33,000 giving an ROI of 11.7 years ($35,000/$3,000).

At a glance, that looks pretty good - only 3 years added to the ROI and then bigger savings. BUT we'd actually only be gaining an additional $500 saving per year for an additional $13,000 spend. So the true ROI for the battery component is actually 26 years ($13,000/$500), which would be beyond the reasonable life expectancy of the Powerwall 3. It took me a bit to get my heads around how that maths works (because looking at it one way looks great, but looking at it the other way looks terrible), but I'm pretty sure I'm correct.

The calculations would probably be similar for a non-Tesla battery,

Unless you can run a model on a reasonably fine time base then those models are pretty useless. I was able to source production data for a nearby site (then correct it for PVpeak, orientation and slope) and I had consumption data down to 5 min resolution from our own meter so could build an accurate model across 12 months showing the net import/export at each 15 minute period. Then I could plug in various tariffs and come up with an estimated savings figure.

I have since validated it with real data from the last year which showed my modelling was a bit low for gross PV output.

3 months after the PV was installed I put in battery to time shift peak consumption, so we now self supply >95% of peak consumption. The advantage is we run our house as a house, not as a power optimization appliance.

Otautahi Christchurch

wellygary

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#3462279 17-Feb-2026 17:08

mark0x01:

Looks like they have all done the caculations so they get the most benefit from our solar.

Your buy rate is going to be capped by the cost of commercial solar, that is competing with you...

Meridian's Ruakaka solar farm is expected to be producing at "$97 /MWh (9.7c/unit) levelized cost of energy (real, 2025)."

https://www.meridianenergy.co.nz/public/Investors/Reports-and-presentations/Investor-presentations/2024/ruakaka-solar-announcement-March-2025.pdf

Paul1977

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#3462281 17-Feb-2026 17:23

fastbike:

Unless you can run a model on a reasonably fine time base then those models are pretty useless. I was able to source production data for a nearby site (then correct it for PVpeak, orientation and slope) and I had consumption data down to 5 min resolution from our own meter so could build an accurate model across 12 months showing the net import/export at each 15 minute period. Then I could plug in various tariffs and come up with an estimated savings figure.

I have since validated it with real data from the last year which showed my modelling was a bit low for gross PV output.

3 months after the PV was installed I put in battery to time shift peak consumption, so we now self supply >95% of peak consumption. The advantage is we run our house as a house, not as a power optimization appliance.

I've taken 12 months worth of power consumption down to 30min resolution. Fed that along with as many details as I could about the proposed inverter, solar panels, orientation, roof pitch, location etc into ChatGPT for it to calculate estimates.

So our consumption data is very accurate, but some assumptions will have been made about what the solar generation will look like. I think it should be reasonably close to reality.

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