Solar Panels Question

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#1860664 8-Sep-2017 08:30

networkn:

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

...

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

I've been putting off our own solar installation because I want at least 10kWh of battery storage along with it....and the house isn't built yet that we will install it on. My "perfect" system would be a Tesla (or possibly Monier) solar roof with 30kWh of battery.....so we could run all evening on stored power, including charging the car a bit.

For me, a lot of value in solar is having the power there when the grid fails and there is a black-out. Our life will go on as normal until it comes back on. That is worth a premium to me. I also think if enough of us go solar then we won't have to help fund large, new power projects because they just won't be required.

We did it ourselves, a wee bit at time. All of us. A new government with a real desire to reduce emissions could change a lot of things and make this easier for everyone.

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tdgeek

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#1860671 8-Sep-2017 08:39

Linuxluver:

networkn:

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

...

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

I've been putting off our own solar installation because I want at least 10kWh of battery storage along with it....and the house isn't built yet that we will install it on. My "perfect" system would be a Tesla (or possibly Monier) solar roof with 30kWh of battery.....so we could run all evening on stored power, including charging the car a bit.

For me, a lot of value in solar is having the power there when the grid fails and there is a black-out. Our life will go on as normal until it comes back on. That is worth a premium to me. I also think if enough of us go solar then we won't have to help fund large, new power projects because they just won't be required.

We did it ourselves, a wee bit at time. All of us. A new government with a real desire to reduce emissions could change a lot of things and make this easier for everyone.

We will be getting PV soon, Im looking at 6kW+. A 20kW battery would be heaven for evenings, but the price is an arm and half a leg. But you cannot run solar PV off grid unless you have some other circuitry? I dont think standard home solar will work off grid or in a power cut. Not sure what happens to the unused power in a power cut though

tdgeek

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#1860674 8-Sep-2017 08:55

networkn:

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?

I get $622 per year, based on 20% loss from circuitry, AC/DC conversion etc, for 2000 annual sun hours, if you use it all. Less efficiency from early and late sun lets say that bring it back to $500. You will also generate on non sun hour days, light cloud etc, but not as much.

1. 10 year payback seems normal from my research, thats a good ROI, tax free.

2. Factor in when its paid off, you get an infinity ROI, $500 per year for zero capital outlay. They last a long while, 15, 20 25 years

3. Add in power company price increases

4. Timeshift anything you can. If you don't do daily washing or dishes, move as much as you can to sun days. You have a pellet fire and no heatpump as well? If you say had a heatpump, in sunny winter days you can offset some pellet fire use by running a heatpump on low in the afternoon.

Linuxluver

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#1860676 8-Sep-2017 08:58

tdgeek:

We will be getting PV soon, Im looking at 6kW+. A 20kW battery would be heaven for evenings, but the price is an arm and half a leg. But you cannot run solar PV off grid unless you have some other circuitry? I dont think standard home solar will work off grid or in a power cut. Not sure what happens to the unused power in a power cut though

I'll have to look into that.

Even if i need to have a switch to swap over then I'll do that.

At the moment I have a line-interactive UPS in front of some LED desk lamps (on extension cords in seconds) and the Internet router and a couple of NAS boxes. If the power goes out, one light and the NAS and router stay on....and I can add other lights to the circuit as required. It worked a treat last week when the power went out for an hour and a half. The rest of the street was in darkness.......just our house with lights on. The UPS got down to about 30%...so I reckon I have just over 2 hours there. I'll get a bigger UPS. :-)

I would hope I could put any solar and power storage in line with something like the UPS so that it can be used as required....preferably automatically, but I'm happy to unplug and thing and plug in another thing if I have to.

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Hammerer

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#1860705 8-Sep-2017 09:48

tdgeek:

3. Add in power company price increases

I wouldn't be including any increase in retail prices. The current market is pretty flat and many of us are paying less year on year. A decade ago the industry correctly forecasted the current situation and I'm confident that they're correct when they forecast flat prices for the next decade.

See the MBIE retail and wholesale price surveys and forecasts, e.g. http://www.mbie.govt.nz/info-services/sectors-industries/energy/energy-data-modelling/statistics/prices/electricity-prices

You should also be doing a sensitivity analysis to see what happens if prices go down by 10%. That is if you really want to ensure that you will get a return.

tdgeek

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#1860706 8-Sep-2017 09:53

Hammerer:

tdgeek:

3. Add in power company price increases

I wouldn't be including any increase in retail prices. The current market is pretty flat and many of us are paying less year on year. A decade ago the industry correctly forecasted the current situation and I'm confident that they're correct when they forecast flat prices for the next decade.

See the MBIE retail and wholesale price surveys and forecasts, e.g. http://www.mbie.govt.nz/info-services/sectors-industries/energy/energy-data-modelling/statistics/prices/electricity-prices

You should also be doing a sensitivity analysis to see what happens if prices go down by 10%. That is if you really want to ensure that you will get a return.

Thanks, good to know

Sounddude

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#1860715 8-Sep-2017 10:17

The University of Canterbury made a very good solar calculator for NZ conditions.

https://www.energywise.govt.nz/tools/solar-calculator/

Worth looking at

wellygary

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#1860716 8-Sep-2017 10:18

Hammerer:

You should also be doing a sensitivity analysis to see what happens if prices go down by 10%. That is if you really want to ensure that you will get a return.

Yeah, the big question with regard to such an investment is Tiwai, - which no one can pick in the short term,

Bbut in the long term, provided globalisation continues, Tiwai will get pushed out as an inefficient producer and closed.....

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#1860722 8-Sep-2017 10:36

On checking I found that wholesale prices are expected to increase more than was forecast last time I looked but retail prices are expected to be relatively level for the next five years.

Lower demand growth and an excess supply of committed new generation should put strong downward pressure on prices for next the decade. Even if new investment is needed from 2017 (as in the High Growth sensitivity), the availability of new renewable generation at around 9 c/kWh (real $2011) should limit real wholesale price increases.

I had a look at the MBIE "Energy Insight 2012" and the "Electricity Demand and Supply Generation Scenarios 2016" which include several scenarios including a high uptake of solar PV and electric vehicles. They can be found at http://www.mbie.govt.nz/info-services/sectors-industries/energy/energy-data-modelling/modelling/new-zealands-energy-outlook/electricity-insight

networkn

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#1860725 8-Sep-2017 10:38

Using the information I believe to be accurate using the above calculator, we would lose nearly $7K over 25 years!

tdgeek

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#1860735 8-Sep-2017 10:56

networkn:

Using the information I believe to be accurate using the above calculator, we would lose nearly $7K over 25 years!

Your tariff is 19.82c Incl GST? Then a 12% discount? You said 24c which from my Genesis was about that incl GST and after discount

Your buyback is 12c, I think its 8c?

You put daily rate, thats for a solar daily rate if there was one, but you wouldnt include the Genesis daily rate as you pay that anyway irregardless of solar, or does Genesis charge you 94c a day if you have solar?

Your usage is a low user usage, average of about $170 per month. I put 10500 being $100 in summer to $350 in winter roughly, and averaged

Doesnt look right. Your simple payback (not counting interest) is still high as your figures seem to be way too low, IMO

Jase2985

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#1860858 8-Sep-2017 12:55

Sounddude:

The University of Canterbury made a very good solar calculator for NZ conditions.

https://www.energywise.govt.nz/tools/solar-calculator/

Worth looking at

it doesnt take into account a battery system, nor a split system (some panels facing a different way)

Jase2985

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#1860865 8-Sep-2017 13:03

@tdgeek:

We will be getting PV soon, Im looking at 6kW+. A 20kW battery would be heaven for evenings, but the price is an arm and half a leg. But you cannot run solar PV off grid unless you have some other circuitry? I dont think standard home solar will work off grid or in a power cut. Not sure what happens to the unused power in a power cut though

A system that comes with batteries will most likely have a hybrid inverter, which has a current sensor on the input power line, and when that looses power in a power cut it will stop the system from "selling" back any power to the grid. this means that any power generated or stored with your system will be kept in there.

the only downfall here is that the inverter will be about 5kw, which means you cant supply your whole house from it. so you will likely split up your whole house into 2 switchboards, one for non backup power, things like a electric hot water cylinder, washing machine dryer, heavy use items, and one for backed up power, is some/all lighting, fridge, tv, pc, networking equipment etc, so less draw than the rating of the inverter.

this way when the power goes out you will lose the non backed up stuff but still function semi normally at home till the power comes back. you can still generate power for your equipment, still charge and discharge your batteries. when the power comes back it will switch back to normal.

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#1860874 8-Sep-2017 13:20

It may be cheaper to simply recharge batteries with cheaper night rate power if it's available in your area, and buy a $1000 generator to use in emergencies.

A friend of mine spent $14K on a solar system. We worked out that I saved roughly the same amount switching to Flick and time shifting some load, though that was when line charges were cheaper at night.

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#1860881 8-Sep-2017 13:29

timmmay:

It may be cheaper to simply recharge batteries with cheaper night rate power if it's available in your area, and buy a $1000 generator to use in emergencies.

A friend of mine spent $14K on a solar system. We worked out that I saved roughly the same amount switching to Flick and time shifting some load, though that was when line charges were cheaper at night.

I feel timeshifting is very important for solar, otherwise your generating for little benefit, then using when there is no generation. If batteries to last the night or two were a few k that would be perfect, but thats not the case. I timeshift for EK, there is a good amount I can do for the sun. The OP is less suited as he has gas water and cooking and a pellet fire. That smaller unit should all generation to be used, so it should not be as bad as that site shows

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