How many solar panels

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AKLGUY79

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#289435 5-Sep-2021 17:24

Just looking at Solar options.

We use about 600 Units each month according to power Company

Would want a battery as well That charges up of course and runs by solar. But then also connected to the grid so we can sell excess back.

How many panels would I need? How do I calculate this?

How safe is that say if there is a power issues in my area and they need to cut the power to work on the lines. Will me supplying power back to the grid be an issue?

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#2772598 5-Sep-2021 19:27

This is where you go and talk to your electrician who has solar installation exp.

As far as having power when there is an outage, unless you specifically have a group of circuits feed off the inverter that is dedicated to provide power in an outage you will have no power if there is an outage - by law the inverters must cut power to the grid when the grid goes out.

Scott3

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#2772634 6-Sep-2021 00:33

A fairly crude calculator is here:

https://www.branz.co.nz/photovoltaic-generation-calculator/

As a rule of thumb ever 1kW of panels will generate 1,100kWh (units) per year in Auckland. Less if panel angle is sub optimal. But that is stacked towards summer when domestic power consumption is typically lower.

You will need to have an electrician install the system, And they will make sure there is no risk of your system back feeding in a power cut. Most gird tied system's just switch off if there is a power cut, but you can get systems with an automated grid isolation switch, that will automatically fall over into island mode in the event of a power-cut (safely isolated from the grid)

Another tool:

https://tools.genless.govt.nz/individuals/solar-tool/

Example pricing:

https://tools.genless.govt.nz/individuals/solar-tool/

Batteries are kind pricey. A Tesla power-wall 2 (13.5kWh usable, 5kW continuous power) runs at $17,000 + install. A Panasonic 85kWh / 2kW attery runs at $13,000

jonb

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#2772646 6-Sep-2021 08:44

4-5kW is the standard for normal residential, I have a 10 yr old 4kW system in Otago, and a woodburner with wetback for main heating and have <$100 annual electric bills after 8c KwH feed-in, with <200KwH usage in the winter. Having a battery sounds great but doesn't stack up for most users currently, and the less electric you you the less the business case for it stacks up, certainly for me it wouldn't. Heating water is about 1/3 the average electric bill, I almost exclusively heat by solar or wetback.

eonsim

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#2772671 6-Sep-2021 09:43

Batteries don't really make economic sense at the moment. However, if you want one for off-grid support or worried about blackouts then it may make sense to you. As others have said you will need to get an electrician to set you up with an islanding system that automatically cuts the house off from the mains lines during a power cut.

As for how many panels, probably as many as you can fit on your roof facing either north, east or west. After a battery and the installation costs for a system the actually cost of the panels is a fairly minor component in which case you might as well stick on as many as you can. More likely to end up unhappy you didn't put enough panels on than too many (if you can afford it). If you want a rough estimate you can have a look at https://pvoutput.org find some NZ based systems in a similar region to you then look at what they generate in a month for June and January then scale appropriately for your use.

You may also want to look at Solar diverters if your using a hot water cylinder to maximize the use of the power you generate. Also a smart meter can be well worth it to see how your doing with energy use, production, export and self consumption.

timmmay

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#2772676 6-Sep-2021 09:55

jonb:

with <200KwH usage in the winter

That's pretty low usage. We use about 2000kwh per month in winter, but we keep our house pretty warm with heat pumps. A fireplace would obviously reduce that.

CYaBro

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#2772680 6-Sep-2021 10:12

timmmay:

jonb:

with <200KwH usage in the winter

That's pretty low usage. We use about 2000kwh per month in winter, but we keep our house pretty warm with heat pumps. A fireplace would obviously reduce that.

Wow I thought we used a lot of power, and we work from home too!

Just looking back at the last few months and we've used 817kWh, 925kWh & 907kWh.
The most we've used in a month is 1056kWh and that was 11 April 2020 - 11 May 2020 so a lot of that time was during the first level 4 lockdown so there was 4 adults and 2 kids here.
I think we'll beat that this month with the lockdown, since it is colder and again there's 4 adults and 2 kids here. Normally only 2 adults and 2 kids but the in-laws are stuck with us again for lockdown.

We do use a wood burner but I have a heat pump in my cabin/office that I use most days during the week, and we have one in the house too but that doesn't get used much as it's in a very strange place! :)

Opinions are my own and not the views of my employer.

timmmay

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#2772685 6-Sep-2021 10:31

Double checked. July 1800kwh, August 1900kwh, for comparison Jan is 1000kwh and Feb s 750kwh. We have an old, well insulated house and we like it about 23 - 24 degrees and I prefer light clothes inside. Working from home, 2 adults one child. About 20% of that power is free with Electric Kiwi.

FineWine

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#2772687 6-Sep-2021 10:34

eonsim:

You may also want to look at Solar diverters if your using a hot water cylinder to maximize the use of the power you generate. Also a smart meter can be well worth it to see how your doing with energy use, production, export and self consumption.

We are very happy with our Harrisons system. During this year which is our first winter, we have halved our power bills and during the second half of summer when we had it installed we were in credit.

Here are a couple of other forum topics:

We have solar PV panels, what Hot Water cylinder and methods to maximise use

Solar Power Energy Solutions

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

jonb

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#2772760 6-Sep-2021 11:21

timmmay:

Double checked. July 1800kwh, August 1900kwh, for comparison Jan is 1000kwh and Feb s 750kwh. We have an old, well insulated house and we like it about 23 - 24 degrees and I prefer light clothes inside. Working from home, 2 adults one child. About 20% of that power is free with Electric Kiwi.

My youngest is 13 so no toddlers to keep warm, main living area about 20 maximum and bedrooms about 16 with heat transfer, I'm fine with that but others won't be :)

Timeshift a lot of cooking, dishwasher and washing machine etc to daytime, evening electricity mostly lighting, TV and electric blanket some nights if kid grumbles.. $500 a year in wood on the flip side but still pretty good going. Banned electric heaters only dehumidifier.

Feed in last month was 233kWh (only about 10 cloudy days!) which was $18.60 credit at 8cents. Peak feed in summer is 500kWh per month about $40 credit. As others have said, anything you can do like a solar diverter for water or timeshifting is better than feed-in credit.

timmmay

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#2772826 6-Sep-2021 11:39

We'd freeze at 20 degrees! We'd just about be wearing gloves. We keep bedrooms at 21 degrees overnight, 22 for the 4 year old. I've read 18 degrees is the recommended minimum even at night. We find many NZ homes poorly insulated / heated.

PolicyGuy

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#2772874 6-Sep-2021 12:46

I'd have to put all the duvets, quilts and other winter bedding away if I kept the bedrooms as hot as 18 degrees. That's a ridiculous temperature for a moderately cool climate.

I only swap from 'summer ' to 'winter' when the overnight minimum temperature is consistently less than 10 degrees.

And a daytime temperature of 20 degrees or more is definitely 'shorts weather', 25 is unquestionably 'hot' and 30 is Too Bloody Hot.
Glad I don't live in Straya

timmmay

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#2772910 6-Sep-2021 13:25

We just the same bedding summer as winter, lightweight.

Quinny

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#2772919 6-Sep-2021 13:48

I did the whole solar thing in canterbury last year including Tesla Powerwall 2. Spent $36k (QV added 40k to my rateable value). BEST decision ever made.

This is the public site https://monitoringpublic.solaredge.com/solaredge-web/p/site/public?name=Quinny&locale=en_US#/dashboard

I went with the best panel LG Neon2 and have 18 of them. In 10 years time the system with still be within 3% of the current output - this mattered to me. The system was designed to account for a house using 20-25kw a day which is over your 600 a month. I have gas hot water and a massive gas fire on reticulated. The house is full of electronics as well as 4 heat pumps as I hate being cold.

I also used the Westpac 10k interest-free for 5 years Winter Warm up loan. Happy to chat anytime or if close to Rolleston you come have a look.

Nate001

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#2772928 6-Sep-2021 14:12

Quinny:

Spent $36k (QV added 40k to my rateable value). BEST decision ever made.

I'd be gutted if this happened, extra rates!

mattwnz

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#2772939 6-Sep-2021 14:32

Quinny:

I did the whole solar thing in canterbury last year including Tesla Powerwall 2. Spent $36k (QV added 40k to my rateable value). BEST decision ever made.

This is the public site https://monitoringpublic.solaredge.com/solaredge-web/p/site/public?name=Quinny&locale=en_US#/dashboard

I went with the best panel LG Neon2 and have 18 of them. In 10 years time the system with still be within 3% of the current output - this mattered to me. The system was designed to account for a house using 20-25kw a day which is over your 600 a month. I have gas hot water and a massive gas fire on reticulated. The house is full of electronics as well as 4 heat pumps as I hate being cold.

I also used the Westpac 10k interest-free for 5 years Winter Warm up loan. Happy to chat anytime or if close to Rolleston you come have a look.

HOw could they add 40k to your RV? Doesn't QVs RV specifically exclude chattels? How would they even know you added them?

I know a house that sold which had solar panels, but the owners took them with them when they sold it, as they were paying them off over 20 years. .

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