Solar Panels Question

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#1860886 8-Sep-2017 13:35

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.

you must have been paying quiet a lot before hand. even over 10 years thats $1400 per year, $116 per month, thats a aweful lot.

that would be about 1/2 of our current powerbill.

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#1860887 8-Sep-2017 13:36

With EK "free hour of power" and a fast charger you could probably do well, though the cost of batteries and the system is still probably far more than you'd gain.

Transpower said something about battery banks at substations possibly being a better option to address peak load than firing up expensive power stations. There was an indication that batteries were still too expensive, but may become economic in the next 5-10 years.

I wonder if there's any other way to store energy at home. A miniature flywheel? Heating salt? Probably not practical.

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#1860919 8-Sep-2017 13:50

Jase2985:

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.

you must have been paying quiet a lot before hand. even over 10 years thats $1400 per year, $116 per month, thats a aweful lot.

that would be about 1/2 of our current powerbill.

They have three hot water cylinders and a spa pool, which soaks up a good fraction of the generation.

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#1860921 8-Sep-2017 13:53

timmmay:

Transpower said something about battery banks at substations possibly being a better option to address peak load than firing up expensive power stations. There was an indication that batteries were still too expensive, but may become economic in the next 5-10 years.

I imagine that lots of people are watching South Australia with interest....

Although Vector also have a 2.3 MWh set up at Glen innes, so that will be looked at closely too

networkn

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#1860931 8-Sep-2017 14:13

tdgeek:

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

According to our bill we pay 19c . If we stay connected to the grid, which is our only option, our daily charge is $1 give or take a few cents. I am not sure if that is supposed to be added there specifically or not. It makes a huge difference of 5K. Without that there, we are losing 1700 at the 25 year mark. The panels are good for 30 years, but I'd imagine they would need to be replaced before that, along with other maintenance which is required.

Genesis told us 12c for buy back.

I can't see living with a $1700 debt after 25 years for the solar solution.

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#1860940 8-Sep-2017 14:28

networkn:

According to our bill we pay 19c . If we stay connected to the grid, which is our only option, our daily charge is $1 give or take a few cents. I am not sure if that is supposed to be added there specifically or not. It makes a huge difference of 5K. Without that there, we are losing 1700 at the 25 year mark. The panels are good for 30 years, but I'd imagine they would need to be replaced before that, along with other maintenance which is required.

Genesis told us 12c for buy back.

I can't see living with a $1700 debt after 25 years for the solar solution.

Ok. You mentioned 24c. I was at Genesis, that was 26.6 less 10% = about 24c, plus 33c daily.

Still doesn't sound right at that website, I know people who have PV, they love it, one has a record of 34kW on one day, last Dec 31 I think it was. $30 bill. My plumber had a large credit still, or so he says

And the others here seemed to be different. When I get serious I will look at my hourly usage, as I will know exactly whats causing it, and assess the benefit there, plus timeshifting. That will be very accurate for me, as its real world. Hard to guess what the website is using to calc its numbers. At a 10 year payback, which I often see online, its very wortb it

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#1860942 8-Sep-2017 14:30

I'd be fine with a payback over 10 years, not longer. I'll double check the numbers.

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#1860949 8-Sep-2017 14:41

Here's another issue that you may want to consider when looking at storage. The idea of Energy Storage On Invested Energy (ESOI) has appeared to compare different storage technologies to highlight "the importance of reducing the energetic and material demands of electrical energy storage". Basically, they're saying that there is a threshold for supporting our civilisation and most battery systems fail to reach that threshold.

When we looked at solar systems in 2006 the lack of cost-effective electrical storage was one of many reasons for going to solar hot water heating which still looks good when appropriating the benefits of solar energy.

I'm surprised how little change there has been in the economics of electrical power storage using batteries. It continues to be a problem because advances in battery cycle life are not increasing as rapidly as capacities and power output. Research focuses on the latter because, for example, phones and laptops need smaller, more powerful batteries.

http://energyskeptic.com/2015/solar-thermal-esoi-energy-stored-on-invested/

This is a fair comparison (“apples with apples”) between storage technologies since the new figures represent electrical energy that would be produced from the underlying thermal storage.

Technology ESOI

compressed air energy storage 240

pumped hydro storage 210

pebble bed thermal, BRRIMS 62

solar salt, parabolic trough 47

Li-ion battery 10

Sodium-Sulphur battery 6

Vanadium redox battery 3

Zinc-Bromine battery 3

Lead-acid battery 2

The simple conclusion from the ESOI metric is that geologic storage is excellent, thermal storage is good, whilst electrochemical storage is poor.

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#1860960 8-Sep-2017 15:05

networkn:

I'd be fine with a payback over 10 years, not longer. I'll double check the numbers.

Im really keen on PV. For my own interest I want to reconcile that website to other real world people I know, well one really, as I have all his bills for everything solar, and his power bills, and access to his Grid and PV usage, just to see how that matches up. If I find anything groundbreaking Ill report back.

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#1860987 8-Sep-2017 15:39

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.

The other thing to note is that the power price you pay per kWh is not the actual cost of the power you are substituting by the solar. The physical power you are substituting makes up around 6-8c of the 24c. The remainder is predominately lines charges. The day is approaching where the lines companies will restructure your lines charges so that the per kW rate decreases (possibly to around 15c) and the daily charge goes up 2-3 times or even more. So it is possible the wholesale electricity prices do rise in the next 5 years (if we get more winters like the one we have just experienced) but the cost per kWh for the home user decreases while the daily connection rate increases. So unless you are going to go completely off grid it could leave your investment worth a lot less than you paid for it.

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#1861026 8-Sep-2017 16:12

networkn:

I'd be fine with a payback over 10 years, not longer. I'll double check the numbers.

im pretty confident it would be more than 10 years

tdgeek

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#1861031 8-Sep-2017 16:24

Jase2985:

networkn:

I'd be fine with a payback over 10 years, not longer. I'll double check the numbers.

im pretty confident it would be more than 10 years

Couple of questions

1. I read that we need to deduct 20% for power loss through wiring, inverter, etc. Fair?

2. We know sun day numbers. Would we allow 4 or 5 hours, say 10 to 3, then deduct another 20% to cater for the rise and fall for the early and late hours?

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#1861041 8-Sep-2017 16:51

tdgeek:

Jase2985:

networkn:

I'd be fine with a payback over 10 years, not longer. I'll double check the numbers.

im pretty confident it would be more than 10 years

Couple of questions

1. I read that we need to deduct 20% for power loss through wiring, inverter, etc. Fair?

2. We know sun day numbers. Would we allow 4 or 5 hours, say 10 to 3, then deduct another 20% to cater for the rise and fall for the early and late hours?

are you talking about for your calculations? i have no idea sorry?

from similar system sizes you should be able to get the average kwh per year from it, the one i quoted at 1.16kw, generates about 1600kwh per year

multiply your system size by 1373kwh to give an approximate kwh system generation for Auckland, im guessing this figure is based off actual data from more than one system they have installed so should be fairly robust in calculations.

tdgeek

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#1861048 8-Sep-2017 17:04

BRANZ, https://www.branz.co.nz/PVcalculator

Tried this and got a similar annual kWh figure to the EECA site, about 1700 per year in ChCh, 315 degrees, 30 pitch, so that maps out. EECA is 1890, in ballpark

EECA used PV is $388 plus $21 exported this is 1.5kW solution. On 6k thats 14.6 years (I ignored interest for now) so thats close enough to the 14 it gave me. But my savings over 25 are $5300, but $410 x 25 years is over $10000, a bit odd

Also, the 6k for 1.5kW is $4000 per KW. My mate got 4.33kW 3 years ago for $4000 a kW and this year, another 3 odd kW for $3000 per KW, both full installs (so he has 2 systems) If OP 1.5KW was $4500 then the payback is 11 years, so getting close

Can I assume that a power company deal wont be as sharp as a deal directly with a solar company? Demand is not high, its still niche, so another party clipping the ticket isnt ideal?

I'm looking at Harrisons https://www.harrisonsenergy.co.nz/ as the plumber recommended them, he loves his solar. @networkn might be worth wasting an hour for them to give a quote?

tdgeek

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#1861053 8-Sep-2017 17:23

Jase2985:

tdgeek:

Jase2985:

networkn:

I'd be fine with a payback over 10 years, not longer. I'll double check the numbers.

im pretty confident it would be more than 10 years

Couple of questions

1. I read that we need to deduct 20% for power loss through wiring, inverter, etc. Fair?

2. We know sun day numbers. Would we allow 4 or 5 hours, say 10 to 3, then deduct another 20% to cater for the rise and fall for the early and late hours?

are you talking about for your calculations? i have no idea sorry?

from similar system sizes you should be able to get the average kwh per year from it, the one i quoted at 1.16kw, generates about 1600kwh per year

multiply your system size by 1373kwh to give an approximate kwh system generation for Auckland, im guessing this figure is based off actual data from more than one system they have installed so should be fairly robust in calculations.

I was meaning losses from wiring and from sun angles, but the numbers are close with the two geographical generation calculators so thats ok

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