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Topic: Payback on solar power systems in NZ


This comment was made about the following article. Click on the title to view the article.

Solar Power in NZ - What is the payback?

This is the most common question we are asked on the subject of solar power systems. People are naturally curious about a technology that can produce a long-term supply of electricity with no continuous financial input, environmental side effect, or lifestyle change. Yet industry, consumers, and government only seem able to rela...
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by Ecobob.co.nz 14 Nov 11, 139 replies : Last Post Sort by:
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306 posts
Payback on solar power systems in NZ 
Posted 14 Nov 11 9:44 PM
This is a great article by Mike Bassett-Smith of Powersmart solar on the current pay back time on investing in solar panels for your a building / house in New Zealand:

http://www.ecobob.co.nz/EcoArticle/2319/0/Solar-Power-in-NZ--What-is-the-payback.aspx
Payback on solar power systems in NZ


128 posts
Re: Payback on solar power systems in NZ 
Posted 14 Nov 11 11:13 PM
The payback period is determined by the buy back price for excess power your system exports back into the grid, currently 1 supplier has a 1:1 deal, the others are a lot worse, unfortunately there is nothing to stop the energy supplier changing these conditions to the point where it is not economic to install.

Perhaps Power smart can supply some more details on long term outlook for buy back ratios. NZ is not subject to govt enforced schemes as common in other developed countries, so there is no certainty in any payback.

15 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 12:21 AM
1. The reason people look at payback periods is to provide a metric against other energy-saving measures. If someone is prepared to invest $15K or more in making their home more energy efficient, how should they spend that money? Is it better spent on home insulation, more energy efficient heating, and perhaps solar hot water? Payback periods provide a useful metric for comparing these options.
2. Government enforced schemes don't make sense because although investment in solar MAY be economic for some home-owners, it is economic in part because they only have micro options available to them. Macro electricity generation projects, even renewable ones, are cheaper than house-by-house solar generation. Subsidising less efficient electricity generation does not make economic sense.
3. The author has used US research on increase in appraisable value. Unfortunately, there is no evidence that that research applies here, nor any local evidence that investment in home energy efficiency measures provides any return on resale. I wish it did, and hope it may in years to come, but it is not yet the case. Therefore, I think the author's inclusion of this return in his case is erroneous.

334 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 7:49 AM
3kW for $15k works out at $5 per Watt peak (PV systems are normally "named" using Wp). And this system does not have storage batteries (price is too low by half) - so feeds straight into the grid.

For Auckland, the annual average daily peak sun hours measured over a year (and based on years and years of insolation data) is about 4 - so 4 peak sun hours a day x 3 kWp gives 12 kWh a day on average, 365 days a year - so about 4300 kWh a year output from a 3 kWp system as the article says.

The article uses "simple payback" - rather than taking into account the time value of money. To be really comparable, the simple payback needs to be converted to a net present value (NPV), to take into account whether you are really better off putting money into the bank or putting it into a PV array to lower your power bills.

Every single conventional power generating technology today works out cheaper than the power produced by this particular 3kW $15,000 example, even though PV requires no fuel. This is because every other conventional power generating technology can work for more than 4 hours a day. All of these other technologies are cheaper for the time being, even when any fuel required is taken into account. But PV prices will keep falling, so at some stage within the next 2 to 3 years, it would be a no-brainer to install PV.

Further, the assumption that prices will keep on increasing is not a valid assumption IMO.

IMO prices will increase first to keep in step with inflation, but also to trend towards the most expensive means of replacement power generation.

As NZ wind turbines sort their maintenance regimes out to reflect the incredible resource we have here (wrecks all the bearings and wearing parts of machines not built for our high capacity factors), and as PV system prices fall, these technologies will place a limit on what the retail power price will be. This is especially since PV can be installed on a home and avoid the doubling of transmission line charges coming through over the next 4 years.

The Herald printed an article on Oct 21 which was originally from The Economist, noting among other things that by the end of this year, the average panel price could be US$1.10 a Wp:
http://www.economist.com/node/21532279

This would give a landed NZ shop retail price of about $2.80/Wp to $3/Wp including GST - still need to add the DC to ac power inverter and auxiliaries - but this would be about $11,000 - $12,000 retail by the end of the year. (Of course suppliers in NZ can't offer this so soon, but it is coming nonetheless).


334 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 7:52 AM
<< but this would be about $11,000 - $12,000 retail by the end of the year>> from above post: for a 3kWp system

63 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 8:32 AM
By importing it is possible to come close to the $4/Wp quoted above (i.e. $12K/3kWp) as prices are being discounted in the US at least. We're installing a 5kWp BP panel based system and will come close to this target.

222 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 11:06 AM
I have no doubt that PV will become one of the predominant ways of supplying energy and almost every household will utilise it. The cost of solar cells has been following a kind of inverse Moore's Law for a couple of decades (except for a period where there was short supply that later rejoined the trend line). This is only likely to continue as manufacturing abilities and techniques have nowhere near been exhausted. In addition it's "plug and play" simplicity must be a big drawcard (no liquids or gases, no moving parts).

The obvious way forward long term is to marry solar capacity with "storage' type energy resources such as hydro and geothermal coupled to a "smart" electricity grid. It is key responsibility of the government to ensure that is a smooth relationship.

Just when a mass movement to solar occurs is a good question. Some factors that may affect Mike Bassett-Smith's arguments are the stagnation in electricity demand due to factors such as energy efficiency and the economy, the declining price of solar making it a sensible choice to delay implementation (that declining price also affects value seen in existing solar installations) and the framework of our current supply system which may require regulatory changes to allow solar to succeed.



128 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 12:03 PM
>> It is key responsibility of the government to ensure that is a smooth relationship...

From the above post, neither of the current or past governments have shown any acumen in getting the electricity situation in NZ to a point favorable to the consumers. The reforms carried out in the past have failed totally and now with the impending sell off of the main generators that will be the end game, there will be no driver for industry cohesion of items like smart grids etc.
Once private industry owns the generation and profits are required by shareholders, then expect the costs to the consumer to sky rocket.
This situation may not help private solar grid tie installations as the industry determines the buy back price, not the govt, so they can dictate a buy back at the generation wholesale cost which is about 1/5 of the retail purchase cost. Unless solar generation approaches these costs then it will never be economic to install.

11 posts
Re: Payback on solar power systems in NZ 
Posted 15 Nov 11 7:44 PM
Just a couple of points that I am not sure of;
1- What effect would having an extra $15,000 on the mortgage have as far as payback time?
2- Would installing a $15,000 solar system on a $500,000 house increase its selling price to $520,000?

15 posts
Re: Payback on solar power systems in NZ 
Posted 16 Nov 11 1:11 AM
1. So long as interest rates stay below the 7.7% (after tax return) rate, the effect of adding the $15K to the mortgate won't affect a properly calculated payback period, as that payback period should include an adjustment for "opportunity cost" (i.e. what return you would have got if the money had been in the bank instead). Unfortunately it's not clear whether the author has included this in his calculations.
2. No, there is no NZ evidence that installing a $15K solar system on your $500K house will increase its selling price to $515K, let alone $520K.

170 posts
Re: Payback on solar power systems in NZ 
Posted 16 Nov 11 6:51 AM
Rather than paying $15,000 to generate 4000kW hrs a year, it is far better to spend $3000-$6000 on solar or a hot water heat pump - as either of these technologies can save 4000kW hrs a year.

Only if your house is paid off and you have a spare $15000 lying around and you are a high rate taxpayer do the figures stack up.

The installed price needs to halve to start generating real interest,

58 posts
Re: Payback on solar power systems in NZ 
Posted 16 Nov 11 11:33 AM
Caziques, On a simple capital invested costing your assumption is correct but you have not allowed for the limited life of a heat pump versus the much longer life of PV. Any reputable module will carry a 25 year performance warranty with an expected working life of up to 40 years. What is the effective life of a heat pump? I know of two large units that were not able to be repaired at 5 years old because the control boards were no longer available so they were replaced. Compressors still good but now useless! Most people in the industry I talk to give heat pumps a life of up to 10 years and then rip it out and replace. No longer a good life cycle cost compared to PV!

170 posts
Re: Payback on solar power systems in NZ 
Posted 20 Nov 11 9:27 AM
"What is the expected life of a heat pump?"

What is the expected life of a fridge? Heat pumps certainly have parts that go wrong, and I am aware of installations which are not cost effective.

However, the chances are that a hot water heat pump used for heating water or heating a house will pay for itself (in simple terms of energy savings) in around five years, after that it doesn't matter too much. Hopefully better/cheaper technology will be around, perhaps cost effective PV

For many people looking 10-20 years ahead is not really an option.

BTW how long do grid tie inverters last?


58 posts
Re: Payback on solar power systems in NZ 
Posted 20 Nov 11 3:15 PM
"However, the chances are that a hot water heat pump used for heating water or heating a house will pay for itself (in simple terms of energy savings) in around five years"

And some of my customers have done the numbers for themselves and figure between 7 and 10 years ROI for their grid tie systems. Not my numbers, theirs. With the long working life these PV systems represent a much better investment than a HW heat pump.

Quality GT inverters have no moving parts, except maybe a fan, so life expectancy is long. Heat is the main killer and poor installation can contribute to early failure. Properly installed there is no reason why a GT inverter can not last as long as a battery based one and I have seen some out there between 30 and 40 years old, still going strong. Sure, not all as again poor installation and environmental factors can accelerate corrosion and aging.

63 posts
Re: Payback on solar power systems in NZ 
Posted 20 Nov 11 3:33 PM
"What is the expected life of a fridge? Heat pumps certainly have parts that go wrong, and I am aware of installations which are not cost effective."

If you are assuming that a heat pump will have a similar life to that expected from a fridge bear in mind that fridges are not normally installed outside in our maritime climate as HPs are. Your estimate of 5 years life for a HP could well be accurate in many cases.

1 posts
Re: Payback on solar power systems in NZ 
Posted 22 Nov 11 1:48 PM
Hi , Is anyone aware of who offers a buyback service in the welly region ?

51 posts
Re: Payback on solar power systems in NZ 
Posted 27 Nov 11 10:35 PM
Well presented article "Mike Basset- Smith". I await with baited breath as these panels become more affordable.

"Lutba" Mentioned spending the $15000 on insulation, but using Cornerstone Building System Lutba you would be hard pressed to spend that much extra on insulation which is double the R-value of the standard insulated timber frame construction. With a solid wall system you would have 3.6 Rvalue for ceiling batts and especially after the Christchurch Earthquakes Polystyrene to the floor slab is fairly standard. Cornerstone has a perimeter beam along with various poly systems to suit. From energy audits I have undertaken have proved minimal energy use.
With this in mind Mikes savings would only be greater so supportive of his analysis.

"Kiwi Kid" and "Lutba" I am not a banker, however if theses savings were to be be taken off a mortgage capitol I am sure that this would have a very positive affect in further savings. It all depends on how one wants to view something.

If we are to consider the environmental impact as well as cost in the equation, where we are needing to upgrade our national electricity systems, the losses to the atmosphere that occurs in transporting this electricity up & down the country, compared to each property, or group of properties having a suitable solar or solar/wind system, reducing demand.

A future proofing system might consider something along the lines of :-
1. the outlining farms (rather than wind farms per-say), around cities and towns generating extra income and providing electricity to cut down losses therefore lessen the energy
requirement.
2. Government subsidies and /or legislate for new housing, Christchurch could be a great way to start with upping the insulation requirement & appropriate water heating system a home requires very little energy.

Food for thought....

51 posts
Re: Payback on solar power systems in NZ 
Posted 27 Nov 11 10:40 PM
Should have mentioned that the Cornerstone Building system is comparable in price with the insulated standard timber frame so there would definitely be savings in excess of Mike Basset- Smiths analysis which for those who have a mortgage would put a great dent in it...

15 posts
Re: Payback on solar power systems in NZ 
Posted 28 Nov 11 12:17 AM
"Lutba" Mentioned spending the $15000 on insulation, but using Cornerstone Building System Lutba you would be hard pressed to spend that much extra on insulation"

That's rather my point. In general it's going to cost a lot less than $15K to insulate a home, which makes the savings achieved from investing in insulation that much greater than the savings achieved from installing PV.

"With this in mind Mikes savings would only be greater so supportive of his analysis."

Yes, if you've insulated your home you will need less energy to run it, but that's true regardless of your source of that energy, and therefore irrelevant to the cost-benefit evaluation of PV.

"I am not a banker, however if theses savings were to be be taken off a mortgage capitol I am sure that this would have a very positive affect in further savings. "

Saying "I am sure..." doesn't tell me anything. I'm not a banker, but I am numerically competent, and either Mike has not included the cost of borrowing in his analysis, or he's hidden it, neither of which fill me with confidence. It's possible it might still add up, but if so, I want to see the numbers. Based on the numbers I do see, it doesn't add up.

"If we are to consider the environmental impact as well as cost in the equation, where we are needing to upgrade our national electricity systems, the losses to the atmosphere that occurs in transporting this electricity up & down the country, compared to each property, or group of properties having a suitable solar or solar/wind system, reducing demand."

Even widely installed, PV would only meet a small fraction of our growing energy needs, so the national electricity system will still need upgrading, so installing PV would not save those costs. Even so, transmission losses have already been included in calculations of whether subsidising PV is economically sensible.

"A future proofing system might consider something along the lines of :-
1. the outlying farms (rather than wind farms per-say), around cities and towns generating extra income and providing electricity to cut down losses therefore lessen the energy requirement."

As above. Tranmission losses have already been included in the calculation of whether subsidies make sense.

"2. Government subsidies and /or legislate for new housing, Christchurch could be a great way to start with upping the insulation requirement & appropriate water heating system a home requires very little energy."

On this one point I do agree. New housing should be built to the highest possible standard, as history has shown us that New Zealand homes are generally used for a lot longer than the 50 years envisaged when they were built. Increasing insulation requirements and more efficient water heating systems make economic sense. PV doesn't. Yet.

Food for thought....


94 posts
Re: Payback on solar power systems in NZ 
Posted 2 Jan 12 5:56 PM
Excellent thread here. congratulations all. I do have PV, however I agree with those out there who claim that solar electricity (in its current format) is highly Inefficient. better than windpower but still highly inefficient...regardless of cost.

Assuming that electricity prices will rise is not a good argument either. electricity prices arte currently set at what the market is prepared to pay and physically able to pay. That price is fluid and in bad times or plentiful supply, or real competition, or real alternatives, the unit cost of main grid electricity falls.... it has to, has done and will do.. oil is another example of this. Just a couple of years ago we had high oil prices which stimulated alternatives and less consumption which in turn led to prices being reduced.

A main point i'd like to make is that if main grid electricity was cheaper there would be virtually no need for most people to even entertain the idea of installing solar.

Assuming also that a pv system will maintain its efficiency is pie in the sky. I have a friend with a major pv system that is down about 60%on output after just 5 yrs.
A realist will tell you that solar is not cheaper than grid power at present levels when all is taken into acount, and a pv system is not set and forget. For example, batteries require replacement (except for pure grid tie where power is not stored but fed into the grid.)

getting back to my point about solar electricity being highly inefficient, i believe it will be "the new electrics" which will win out eventually...a whole new way of generating power simply and in abundance.


94 posts
Re: Payback on solar power systems in NZ 
Posted 2 Jan 12 5:56 PM
Excellent thread here. congratulations all. I do have PV, however I agree with those out there who claim that solar electricity (in its current format) is highly Inefficient. better than windpower but still highly inefficient...regardless of cost.

Assuming that electricity prices will rise is not a good argument either. electricity prices arte currently set at what the market is prepared to pay and physically able to pay. That price is fluid and in bad times or plentiful supply, or real competition, or real alternatives, the unit cost of main grid electricity falls.... it has to, has done and will do.. oil is another example of this. Just a couple of years ago we had high oil prices which stimulated alternatives and less consumption which in turn led to prices being reduced.

A main point i'd like to make is that if main grid electricity was cheaper there would be virtually no need for most people to even entertain the idea of installing solar.

Assuming also that a pv system will maintain its efficiency is pie in the sky. I have a friend with a major pv system that is down about 60%on output after just 5 yrs.
A realist will tell you that solar is not cheaper than grid power at present levels when all is taken into acount, and a pv system is not set and forget. For example, batteries require replacement (except for pure grid tie where power is not stored but fed into the grid.)

getting back to my point about solar electricity being highly inefficient, i believe it will be "the new electrics" which will win out eventually...a whole new way of generating power simply and in abundance.


94 posts
Re: Payback on solar power systems in NZ 
Posted 2 Jan 12 5:58 PM
my sincere apologies for my error of posting this twice.

63 posts
Re: Payback on solar power systems in NZ 
Posted 2 Jan 12 7:17 PM
So to summarise, a grid tied PV system using good quality panels (BP claim 90% at 12 years and 80% at 25 years) is recommended.

115 posts
Re: Payback on solar power systems in NZ 
Posted 2 Jan 12 8:39 PM
Actually all solar panels for sale at the moment claim around those figures.
The problem will be claiming the warranty from the panel manufacturer in 25 years.
nofear, after 6 years is your friend able to pursue a warranty claim?
My solar off grid system will still produce the rated output ,I started 8 years ago and have grown the system. Average age probably around 4 years. Maybe when I started it produced more than rated output , but back then my equipment was not easy to see the output,

94 posts
Re: Payback on solar power systems in NZ 
Posted 3 Jan 12 6:42 AM
Hi Tearai and harm less solutions,
I will be talking with my friend to see what recourse, if any, he has. You have made a good point about new systems sometimes outperforming their ratings.

I'd also like to say that I am not anti solar electricity and in some cases where main grid power is not an option, solar, in combination with other sources, is worthwhile.

I have enough solar electricity for basic emergency power when the grid fails, but I would not entertain getting too carried away with trying to run all the luxuries on solar electricity.

I suspect that many of these 25yr warranties will mean little. They are promising an outcome, way into the future, on a product that may not have been testesd any where near that length of time. We all remember the inflated claims of eco bulb life spans.

I am very interested in heat conversion into electricity as a possible future power source.

I still believe that steam- generated electricity/ hot water/heating may be the best solution for lifestylers. I/2 a barrowload of wood a day to heat and power 3 homes at once for an outlay of about $13k. The Indian version costs substantially less though I am not certain of the build quality.

 

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