This modular pavilion has a floor area of 154m2.
It has an average daily consumption of about 20kWh . . . . but with all those solar panels its expected energy production is 100 kwh.
OK its efficient but it certainly looks weird.
For each kw of installed capacity of solar panels on average you can expect to generate 3.5kwhrs per day.
This can however vary considerably for a variety of reasons.
On a peak summer day you may be able to generate 6 or 7kw hrs per day.
In winter it can be quite different. typical reasons include:
One of the things that most people don’t realise is that solar panels are ‘team players’.
The power that each panel in a string(circuit) generates is limited by the performance of the worst performing panel in the string.
This means that if one 200w panel in a string of 6 is shaded by as little as 10% the loss can be 120w.
That’s 10% of the total string 6 x the 20w of the single panel)
To minimise this problem you need to ensure:
Any dirt on the panels will reduce the effectiveness so a regular clean will help retain efficiency.
It’s also worth thinking about keeping birds from perching on the top edge and crapping on the panels. (You can get some plastic spikes to fasten to the panels)
Typically panels are at their highest efficiency at a panel temperature of 25degees C.
In the middle of summer the panel temperature can be 80 degrees.
If you panel is mounted to allow better air movement around the panel this will help keep the temperature down, and help efficiency.
Downsizing to a smaller new house for your retirement? Don’t forget to think about solar power.
Last week I revised a post ‘Solar Power is it Worth It?‘ but if you are approaching retirement, like me, there can be an even bigger financial advantage in having solar installed.
Because we are both out at work during the weeks I calculated that with a 1.5kw system costing around $3,000 panels we will save:
See the original post to see how I arrived at these figures
After retirement its likely that our weekday usage patterns will be more like the weekends so our annual savings are expected to be 365 x $1.40 = $511.
I am assuming that you will have some money from superannuation, but not enough to mean you won’t be eligible for a state pension.
If you have more assets then the Government limits your pension. It will be reduced by $39 per annum for every extra thousand dollars. (Basically the government takes the interest)
Invest $3,000 in a solar power system and that becomes part of your house, which is excluded from the governments asset test. You will therefore be eligible for an extra $117 a year pension.
The expected benefit for your $3,000 investment is:
$511 + $117 = $628.
20.9% Return with a Payback of Under 5 years
I don’t know about you but i’m hoping to live a lot longer than 5 years beyond retirement!
For more about solar panels see Sustainability, Solar Power
There is a lot of marketing information around about Grid Connected Solar Panels but not many independant facts. Here’s an example of an evaluation of a basic system for a house.
Weekdays (as we both work and the house is empty during the day) we should be able to put at least 2.5 kwhrs into the grid and use a maximum of 2.7kwhrs running fridges etc)
Income 2.5kwhr @ $0.08 = $0.24
Saving 2.7kwhr @ $0.3152 = $0.85
Benefit = ($0.24 + $0.85) x 260 days = $283
Weekends we probably will only put 1kwhr into the grid as we may well be at home using power for TVs, heating or cooling, etc.
Income 1kwhr @ $0.08 = $0.08
Saving 4.2kwhr @ $0.3152= $1.32
Benefit = ($0.08 + $1.32) x 104 days = $145
Total annual benefit is $428.4
Well there are some 1.5kw systems being advertised now with various rebates which cost less than $3000.
If you had $3000 on term deposit returning 4% that’s $120 a year, which would then be taxed. Alternatively if you put the cost on your mortgage that will mean that you are borrowing $3000 at a rate of around 6%. That’s costing around $180.
From these figures it looks like for the basic system you will be around $250-$310/year better off.
NB. I first did a Cost Review in 2011. Since then the cost of panels, and the government subsidies, have gone down. The cost of power from the grid has gone up. The overall financial advantage is around the same.
Several people have commented that my panels look different to those on other houses.
Most solar PV installations use Mono-Crystalline panels, because they are smaller for the same power rating.
The panels on my roof are Kaneka Thin Film Panels.
Here are the reasons why:
When you see a panel power rating it is based on laboratory conditions with a panel temperature of 25oC.
In Australia, on your roof, the panel temperature is generally somewhere around double the ambient temperature, thus most panels operate above 25oC most of the time.
Typical crystallines panels lose power @ 0.45% per degree C above 25oC.
Typical thin-film panels lose power @ 0.25% per degree C above 25oC.
This means that on a typical 25oC day with a panel temperature of 50oC
On hotter summer days when panel temperature can rise to over 80 degrees the difference will be even greater.
Thin film panels are bigger than mono-crystalline panels means that more of your roof is shaded by the panels helping to keep the house cooler.
Thin film panels have much lower embodied energy than mono-crystalline panels meaning that the energy involved in the production is recovered within two years of use.
Partial shading effects can be quite significant in overall system efficiency. Thin film panels however are less susceptible to shading.
In spite of the above advantages for Thin Film panels the cost per installed watt is around the same as Monocrystaline panels.
More independent information about solar panels in Australian conditions can be found at the Desert Knowledge Solar Centre at Alice Springs
From some of the adverts you see you would think there is only one sort of solar panels…. in fact there are several alternatives.
The type of panels generally available are:
Don’t get too confused by the marketing hype and the quoted efficiencies.
Unless you are have limited space to put the panels the best panel is the one that produces power at the smallest price per watt and will continue to do it for the longest time.
An advantage of having larger, but lower efficiency, panels is that more of the roof is shaded by the panels in the summer. This will reduce the heat gain in the roof space, saving on cooling costs.
The only times that efficiency becomes important is when;
As well as the cost per watt you should also looking for panels from reputable manufacturers that come with a long guarantee (Up to 25 years). Additionally you would be advised to ask for a 5 year installation guarantee.
Since this post was written in 2011 there has been many changes; in subsidies, the cost of systems, and Power Supplier charges. For the an updated post see: Solar Electricity – Is It Worthwhile? (2014)
There is a lot of marketing information around about Grid Connected Solar Panels but not many facts. Here’s how I evaluate a basic system for a house in a Melbourne Suburb.
As we are out of the house for at least half the peak period the cheaper off peak power should more than offset the more expensive peak power so our average power cost should remain similar to our current tariff.
Weekdays (as we both work and the house is empty during the day) we should be able to put at least 2.5 kwhrs into the grid and use a maximum of 2.7kwhrs running fridges etc)
Income 2.5kwhr @ $0.0.265 = $0.66
Saving 2.7kwhr @ $0.2625 = $0.70
Benefit = ($0.66 + $0.70) x 260 days = $353
Weekends we probably will only put 1kwhr into the grid as we may well be at home using power for TVs, heating and cooling, etc.
Income 1kwhr @ $0.265 = $0.265
Saving 4.2kwhr @ $0.1075= $0.45
Benefit = ($0.265 + $0.45) x 104 days = $74
Total annual benefit is $427
(I believe my calculations have been fairly conservative and the actual benefits could be higher) PLUS For every $0.01 of premium rate buy back you will get another $6.24 per annum.
Well there are some 1.5kw systems being advertised now with various rebates which cost less than $3000.
If you had $3000 on term deposit it would now (Jan 2010) be returning 6% that’s $180 a year, which would then be taxed. Alternatively if you put the cost on your mortgage that will mean that you are borrowing $3000 at a rate of around 8%. That’s costing around $240.
From these figures it looks like for the basic system we could be around $187 better off. Even more if you spend less than $3000 or can get a premium buy back rate.
If you are looking to get a system you need to know that there may additional charges for things like:
