Solar Panels Question

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networkn

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Topic # 222991 6-Sep-2017 23:13

So at the home show today we came across Genesis Energy with a stand advertising solar panels in various packages.

I was a little confused by the various options, but it seems that given we aren't really keen to shell for a 4KW battery at 8K or the Telsa Battery for 10K, and that the vast majority of our usage is likely to be between 3pm and 2am, that we might be best with the entry level package of 4 Panels which they say should be good for about $100 worth of power a month. The package was just under 6K, and because we have a mortgage with Kiwibank, we get a 2K discount by way of a loan across 5 years.

Across 5 years, at $100 a month, I work that out at 6K "saved" so the project would essentially be a zero cost at the end. The 2K we get from Kiwibank, the Genesis guy said was likely consumed by Interest they charge, so it's likely we would simply end up with a Interest free loan over that period. It's apparently modular so we could add more panels later.

We aren't sure but feel that solar wouldn't add any value to the resale of our property, but may make it easier to sell.

Our monthly power bill is about $250 a month, and we have a pellet fire for heating, and Gas for Water and Cooking. We have a lot of electronic devices.

Anyone able to comment in not too technical terminology as to the sense in this proposition?

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Reply # 1860070 7-Sep-2017 07:08

We have solar installed as my wife won a prize at one of the home shows that effectively gave us 50% off a solar system. We have 10 panels @ 265W so a 2.65kW system.

ideally I think the true benefit comes when you add a battery but the payback doesn't seem to work out financially at the moment.

The big thing is that you are best to use the power generated by solar than to get any payback from Genesis for the power you put back into the grid. In summer we got about a $25 credit, but winter has been around the $6 mark.

We have changed the way we do things like putting the washing machine and dishwasher on delayed start and putting them on before we leave for work. Ideally you want them to start around 10am but depending on you appliance it depends if you can delay if for that long.

We have gas for hotwater and heating. We have seen our bills half in summer and about a 20% drop in winter.

tdgeek

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Reply # 1860078 7-Sep-2017 07:46

How many kWh is your entry level package?

At $100 per month, that's $3 per day, about 13kWh usage per day, based on the 24.5c net of discount when I was on Genesis. Assume the middle 5 hours is good input to the panels, thats 2.7kW per hour. I think panels are 270W each, which is just over 1kW. Doesn't seem quite right

Plus off course not every day is a great sun day. And the best savings are when you arent using much power, in the summer, and sun isnt great in winter re hours and angle.

Im seriously looking into this to compliment our solar HW (which I love)

Battery wise, I cant justify it. 4kW isn't much when you may use 30 to 40kW per day, and at night, there is some electric cooking, lights, TV's etc. My feelings are PV with no battery, and timeshift anything you can. If you used the 4kW each night on an $8000 battery, thats $1 a day saved, $365 annual saving on 8k.

EDIT

At $6k, its probably 2kW? A friend got a 4.33kW system a few years back at $4000 per kW, and last year added another 3kW (complete system, not add on) for $3000 per kW

tdgeek

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Reply # 1860094 7-Sep-2017 08:46

Before this drops off the list, paging @aredwood he will tell you all you need to know

Jase2985

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Reply # 1860422 7-Sep-2017 16:32

Mercury do a 1.16kw (4 panel) system for 5k, and 4.64kw (16 panel) for 13k, and 4.64kw with 4.8kwh of battery storage for 20k.

they estimate that the 1.16kw system will generate 1593kWh a year, and at 24c/kwh thats about $382 per year if you use it all

networkn

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Reply # 1860427 7-Sep-2017 16:40

Jase2985:

Mercury do a 1.16kw (4 panel) system for 5k, and 4.64kw (16 panel) for 13k, and 4.64kw with 4.8kwh of battery storage for 20k.

Genesis is 1.5KW for $5K it's the one we are looking at.

A workmate and I did some estimates.

2000 Approx Sunlight hours in Auckland Per Year.

Assuming 100% output of 270W x 6 Panels / 1000 for KW/H gives 3240 KW/H Per Year. At 24c per KHW I got $777 maximum savings on a best case scenario. Assuming 66% efficiency, more like $500 or thereabouts, so we would be 8-10 Years before it paid for itself.

It's not outrageous, but not as good as I'd hoped.

Anyone see any flaws in the calcs?

Jase2985

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Reply # 1860454 7-Sep-2017 17:08

yep, you need to take into account how much you will actually use, if your selling it back to the company you are not saving the 24c you are only saving 6-10c.

our base load at home is about .6kwh during the day, so any power generated above that would be sold back at the lower rate.

Aredwood

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Reply # 1860515 7-Sep-2017 19:09

This^^^^^

See how much power you use during the day (especially around midday). Often you can login to your power company website to see 1/2 hourly smart meter usage data. No point in getting a large solar system if you will be exporting most of the power it generates. It can work really well if you have high baseload power usage due to running a home office, home server farm, bitcoin mining etc.

If you have a large electric hot water cylinder, you can get dirvetor controllers. That use excess solar power to heat the cylinder instead of exporting the power. In effect using your hot water cylinder like a battery. And a large hot water cylinder has a way lower cost on the basis of $$$ per KW/Hr of energy storage.

Also are you on a standard user or a low user power plan? As low user plans won't be around forever. (they were a kludge introduced by the previous Labour government in an attempt to help low income households. But only 5% of the savings from those plans go to low income households). So if you are on a low user plan, do the sums on standard user power rates as well. And don't count on even the current low solar buyback rates remaining. There were alot of complaints when the 1:1 buy / sell plans disappeared.

Also not all power companies accept customers who have solar power systems. Flick Electric definitely don't. And AFAIK Electric Kiwi and Pulse Energy don't accept solar customers either. So make sure that you won't get locked in to only higher priced power companies.

And Grid connect solar won't provide power during a power cut. Unless you also have the correct battery and inverter setup.

Myself - I already have solar hot water. And Im slowly building up a solar PV system. But I want to have a backup power system. My solar hot water system was giving me good savings when I was still with Contact Energy. Then Flick Electric appeared. Cheap offpeak power killed the savings from my solar hot water system. (Flick Electric didn't even exist when I installed my solar hot water system). And my solar PV system is unlikely to save me enough on the power bill to repay it's install costs either. Ill just have to write off the losses as the costs of a hobby. (plenty of other hobbies that are far more expensive than solar systems). Although the solar hot water system has given me valuable experience that is handy for my day job. (Im a Plumber / Gasfitter).

richms

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Reply # 1860559 7-Sep-2017 21:01

networkn:

So at the home show today we came across Genesis Energy with a stand advertising solar panels in various packages.

I was a little confused by the various options, but it seems that given we aren't really keen to shell for a 4KW battery at 8K or the Telsa Battery for 10K, and that the vast majority of our usage is likely to be between 3pm and 2am, that we might be best with the entry level package of 4 Panels which they say should be good for about $100 worth of power a month. The package was just under 6K, and because we have a mortgage with Kiwibank, we get a 2K discount by way of a loan across 5 years.

WTF? I have 10 panels, and get about $50 worth of power as reported by the enphase monitoring stuff each month. No way you would get $100 a month out of 4 panels. Unless they were roof sized panels.

Richard rich.ms

redmouse

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Reply # 1860593 7-Sep-2017 22:02

@Aredwood, Electric Kiwi do accept customers with PV systems, but they don't pay for any power you export - https://www.electrickiwi.co.nz/faq/selling-to-electric-kiwi We have found switching from Trust Power to EK worthwhile.

We've had our Solar panels for about a year, 2.9 kW in the Wairarapa. We have generated about 4,000 kWh. Of that we exported/wasted around 1,700 kWh.

networkn

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Reply # 1860604 7-Sep-2017 23:01

richms:

networkn:

So at the home show today we came across Genesis Energy with a stand advertising solar panels in various packages.

I was a little confused by the various options, but it seems that given we aren't really keen to shell for a 4KW battery at 8K or the Telsa Battery for 10K, and that the vast majority of our usage is likely to be between 3pm and 2am, that we might be best with the entry level package of 4 Panels which they say should be good for about $100 worth of power a month. The package was just under 6K, and because we have a mortgage with Kiwibank, we get a 2K discount by way of a loan across 5 years.

WTF? I have 10 panels, and get about $50 worth of power as reported by the enphase monitoring stuff each month. No way you would get $100 a month out of 4 panels. Unless they were roof sized panels.

Wow, that's very discouraging. Did you see the numbers I posted earlier, did I make a mistake on my calculations?

10 Panels must have cost a fortune, all for $50 a month, your payback would be 25 years?

What made you do it?

Stan

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Reply # 1860608 7-Sep-2017 23:21

I made a solar payback calc a while back when I was working in the industry.

https://docs.google.com/spreadsheets/d/1N-KrgeVBAWgxYum4o2OIfJwiSqrhpbMjiyyHa-qf7Sk/edit?usp=sharing

Aredwood

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Reply # 1860610 7-Sep-2017 23:33

@redmouse thanks for the update. Glad more companies are allowing solar PV installs. Hopefully Flick Electric will allow grid connect PV soon. (they say that it is coming).

If you have an electric hot water cylinder, consider adding a PV dirvetor to your system. It will sense if you are exporting power, and use that power to heat your cylinder. Meaning much higher direct usage of your solar generated power. I believe that @Sunmerboy has this system on his own house.

networkn

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Reply # 1860611 7-Sep-2017 23:56

Just checked our day time usage during the week is 0.5 and night time about 1.5

Jase2985

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Reply # 1860627 8-Sep-2017 05:30

One person supports this post

in all honesty if you are going to dive into solar you need to monitor you power properly for a bit

we are using one of these:

http://efergy.com/nz/energy-monitors/online-access/manage-energy-online/engage-hub-kit

Will take a power reading every 6/12/18 seconds and record it on a dashboard, i can pretty must tell you what all the blips and peaks are on the graph.

Its also good as you can get an idea of your base load so you could properly size a solar system from that, which we are planning to do.

At the moment most solar systems have a payback period of about 12-15 years

Jase2985

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Reply # 1860628 8-Sep-2017 05:36

networkn:

Wow, that's very discouraging. Did you see the numbers I posted earlier, did I make a mistake on my calculations?

your mistake is you are assuming you are using all the energy created by the panels 100% of the time, which seldom happens, you might only use 50%-70% of whats created and the rest gets experted.

for us if we were to put 2x290w panels on the roof we would most certianly use all the power from them all the time they are generating power, so the pay pack period would be less than if you overspeced the system and had to sell power back to the grid.

We are looking to go for batteries but this means you need to over spec the system for you base load as you also have to account for charging the batteries during the day. so you need to generate enough power to try to fully charge your batteries even on an overcast day, but maybe not a rainy day.

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