A 410W solar panel. Look at the size of that thing! (image: TopSun)

The Size of Solar panels is definitely increasing, there’s no denying it.

A couple of years ago the average solar panel was 165W. Today the average is about 240W. The biggest one approved for installation in Australia at the time of writing is the whopping Topsun TS-S410. This giant amongst solar panels has these super sized stats:

• Peak power: 410W
• Almost 2m tall x 1.25m wide
• weighs 35kg
• contains 96 solar cells

If anyone has ever spotted any of these monsters on an Aussie roof, please send in some snaps!

If you go to my solar panel comparison tool and sort by size, you’ll see some more super sized solar panels accredited for use in Australia.

But enough of the solar panel envy! Let’s get back on topic … A common question in my inbox is this:

What size of solar panel do I need? I’ve been offered a system with 190W panels and another mob is offering 250W panels. Is bigger better?

Here are the pros and cons of using bigger panels:

Advantages of bigger panels:

• You get a slightly better Watts per m ² because you have more solar cells and less aluminium framing. So you should be able to fit a slightly bigger system on your roof.
• Fewer panels are used for the same sized system, so there are fewer electrical connections, which in theory means a more reliable system.
• Fewer panels means a slightly quicker install.
• Fewer panels means less racking, framing and fasteners, so less embodied energy in your solar system.
• Larger panels tend to be newer stock than the older panels, from more modern production lines.

Disadvantages of bigger panels

• They can constrict your system design in terms of where they will fit.
• They can constrict design as to how they are wired up because they each produce so many volts.
• They are heavier and potentially more dangerous to install on a roof.
• If one fails out of warranty it is going to be more expensive to replace.

So generally speaking, all else being equal, the larger panels (240W+) would be my preference. But if you are being asked to pay a big premium for the privilege of bigger panels, you may as well go with the smaller ones, as they should produce just as much power.

If you are considering putting some solar panels on your roof, then I strongly recommend that you have a physical site inspection before getting firm quotes.

Since I started SolarQuotes over 3 years ago, we’ve handled over 100,000 quote requests and over those years the most frequent complaint I’ve had from people looking for quotes is:

“This solar installer won’t even give me a ballpark price for a solar system! He’s insisting on coming round to my house first!”

I understand the sentiment. If you want really ballpark figures, here are the approximate cost of solar systems. Just be aware that those prices can vary by thousands depending on your home’s layout and the condition of your roof.

If the prices on that page don’t have you running for the hills then the next step in all honesty is to have each solar installer/salesman come round and assess how suitable your home is for solar power.

A word about heavy handed sales tactics

A very valid reason for resisting a site inspection is that you have heard press reports of some solar sales people pressuring people into buying. I believe this is completely unacceptable. I work hard to try and keep solar companies that employ those tactics off SolarQuotes. But in the rare instance that someone referred through SolarQuotes tries to get you to sign anything without giving you the courtesy to go away and consider your options, just contact me. I don’t want to refer companies that use those tactics.

Oh, and whilst we are on the subject, if you ever come across one of the special breed of jerks who try to get you to waive your cooling off period, please kick them out of the door first, second, report them to ACCC, and third let me know so I can out them to the world.

The reality is that 98% of solar sales people and solar installers are really nice people who just want to come round so they can be sure that the recommend a system that suits your electricity usage patterns and your house. Of course they also want the opportunity to impress upon you why their solution is the best, but that is all part of the fun.

Rant over.

Here are the reasons why I recommend a site inspection if you want to end up with a  system that makes you happy:

1) You can look them in the eye and assess their competence by asking some tough questions like these. If they can’t answer them or look panicked, end the visit promptly and move on.

2) It weeds out the ultra cheap and nasty mobs who can’t afford to send someone round, they just wanna flog it, get someone to bang it on your roof and disappear.

3) They need to check the condition of your roof if it is more than 10 years old. It may need repairs before anything is installed. You really don’t want to have to remove your panels to repair your roof a few months/years down the line.

4) Shading. If you have any shade on your roof at all you just can’t assess how much that will hurt your solar power system from Google Earth or Nearmap.

5) Cable Routing. They need to assess how they are going to get the cables from the solar panels to the inverter with as little modification to your house as possible.

6) Your Switchboard. They need to look at your switchboard to see if it needs upgrading and if there is space inside it for an extra circuit breaker.

7) Inverter location. The need to scope out where the inverter can go where it will be nicely shaded, out of harms way, and ideally as close to the meter as possible.

8 ) Panel location. If you are getting a big system (3kW+) then roof space is likely to be at a premium. You should really get a more accurate measurement than Google Maps can provide. Also you may need to split your solar panels over multiple roof areas. If this is the case then you are much more likely to get a better designed, better performing system if the designer can actually visit your home.

Having said all that, you may want a small system, have a recently built home with a massive north facing roof, a modern switchboard and no trees or other shading issues whatsoever. In that case, you could reasonably argue that buying solar without an inspection is pretty low risk. And it is. But even if you are only paying $2,500 for your system, don’t forget that with the rebate, it is $5,500 worth of gear that you will use every day for the next 20 years and an inspection will hugely increase the chance that you get a system that performs well and makes you happy, then a quick inspection is kind of a no brainer isn’t it?

Australian waste management group Veolia Environment Services are very proud of themselves this week as they prepare to celebrate the installing of their brand-new, state-of-the-art solar powered energy source at its Arndell Park facility in NSW.

On Feb.23, the company will be hosting a knees-up to mark the recent installation of the 50 kW solar panel system, which has been added as part of the company’s drive towards boosting its renewable energy source. The project — in collaboration with BP Solar and installed by Solar Technology — is a key part of the Blacktown Solar City project, described, a little breathlessly in a company press release of Feb. 14, as being derived from “…a $94 million Australian Government initiative to help lay the foundations of a sustainable energy future.”

Danny Conlon, General Manager of Veolia Environmental Services, NSW said the solar project “…further solidifies our commitment to reducing our environmental impact through the utilisation of alternative energy sources.”

The recent focus on the so-called collapse of negotiations over the federal large scale solar flagships projects have hit the headlines (and in many cases tried to tip the bucket on solar energy as a viable alternative to fossil fuels). However contrary to the anti-renewables narks’ predictable points of view, the taking up of smaller scale solar energy projects such as that introduced by reputable (and profitable) companies such as Veolia would seem that solar is considered an excellent alternative.

Perhaps more encouragingly, this may be an example of Government incentives for solar actually working. As mentioned, the feds have dug deep into their (well our) pockets, to back the Solar City project, money which looks well spent on this occasion.

So where should the feds spend our hard earned folks? Does this template look like a winner? Veolia thinks so. They are citing the solar energy system as a “huge achievement” and are hoping it will provide an example to other commercial industries who may also be considering taking up the solar option as part of their renewable energy committment.

Short Answer: Probably Not.

Longer Answer:

Ah, the joys of STC prices!

Every so often I get an email from someone who is desperately worried that their solar installer is using the STC price to rip them off.

The suspicion is usually kicked off by one of two things:

1) The “Surrender Your Rights” Clause

The customer has read through the solar contract and has come across a clause that looks like this:

“You unconditionally agree to surrender all your rights to create STCs for the purchased system for the next 15 years to Acme Solar”

When people read a clumsily worded clause like this it conjures up an image of the solar installer laying claim to your precious solar electricity for the next 15 years (and perhaps taking your first born too!) and they are naturally wary of signing any “rights” over to someone else.

The reality is that this daft clause is just a lawyer’s way of saying:

“You grant the installer the right to claim your upfront Federal solar rebate for you so he can reduce the price you have to pay by the rebate amount”

You are not granting the installer any rights to sell your electricity! That is a completely separate rebate called the “Feed In Tariff” and the installer can’t touch it. (Unless you have entered a very special kind of contract called a “Power Purchase Agreement” but that is another story).

So why does the clause say that you have to assign the STC rights for 15 years? Well that is because the upfront rebate is calculated based on how much CO2 your system will offset over 15 years.

Now on to the second reason some people worry that they are getting stiffed by their Solar Installer:

2) Quoting the wrong STC Price

[Note on STCs: For those who don't talk "solar" , STCs are the certificates that make up your federal rebate. Their price fluctuates on the open market. You get about 90 STCs for a 1.5kW solar system, so if the STC price is $20 then you will get a $1800 rebate, if it is $30 you will get a $2700 rebate]

The Common Allegation: The Solar Installer Quotes an STC price of, for example, $25. The canny customer looks up the STC spot price here and sees it is, for example, $28. The customer accuses the solar installer of not giving them a fair price for their STCs. The customer believes they could sell the STCs themselves and get an extra $5 per STC, saving $100′s from the price…couldn’t they?

Not really… There are 2 STC prices in the market place. An advertised “spot price”, and the price that is allowed on your system. The spot price is always higher – by up to $3 at times.

Summary of how selling STCs happens in the real world:

Upon completion of your job, you assign your (Renewable Energy Certificates) RECs to an Aggregator (a third party company) for say $25.

It takes an Aggregator 4 weeks to convert your RECs into sellable “Registered Certificates” – often also referred to as STC’s.

The Government (ORER) charges the Aggregator 50c / REC to convert them.

Once converted to a certificate, the Aggregator then needs to combine 30-40 other jobs / Solar PV Installations to bundle into 5000 STCs  - Now the Aggregator can sell your STCS/RECS on the open market at the current “spot price”.

So the $3 extra they may sell for, includes government fees, admin costs, risk margin and hopefully some profit for the Aggregator.

So if the STC price on your quote is a few dollars less than the current STC spot price, you are not getting ripped off! The installers are just covering the cost of selling the STCs through the STC Aggregator.

Not sure how many SolarQuotes readers caught this fascinating Radio National discussion during the week. Amongst a number of issues raised, it gave a number of insights into the problems facing how Australian governments deal with solar power incentives.

Hosted by Waleed Aly with guests Matthew Wright, executive director of the renewable energy action group Beyond Zero Emissions, and Tony Wood, energy program director at the Grattan Institute, the discussion also included a brief cameo appearance by phone from the ACT’s minister for sustainable development, Simon Corbell.

One of the key discussions was how to implement an effective feed-in tariff, a factor that seems to elude state and federal governments here in Australia almost every time.

Matthew Wright made the key point that incentives for solar in countries like Germany work in a different form which helps give fledgling solar companies the boost they need early on their development cycle, while providing a time frame during which the support is given before being taken away.

Here’s the quote from the Radio National interview.

“If that technology shows that it can actually run down the cost curve, towards the cost of fossil fuels, they say, alright, incentivise it, at day one, at a certain price. Then over a ten year period, or a five year period, it has to get itself weaned off those incentives. Just like a child, that gets weaned off its parents, and goes off and finds its own job,” said Wright.

Only proven technologies than can prove they can compete with fossil fuels are given the go ahead, he continued.

“They have only chosen technologies that can prove, to a technical panel, that they can go down the cost curve. So solar and wind, are completely that. For years and years, they have been paying incentives, and the technologies have been getting cheaper and cheaper and cheaper, and you can see that through the German scheme, which is always paying less every year, for any new installs of those technologies.”

It doesn’t sound like rocket science does it? I stand to be corrected but isn’t this a far superior way of providing government support and incentive than our current “boom and bust” cycle? This is mostly due to the fact that solar incentives such as feed-in tariffs are subject to changes at the drop of a hat — or change in government at election time — thereby robbing solar operators and consumers of any certainty.

The removal of the incentives, planned for 2017, looks like it will come in under the time with subsidies removed by around 2015, according to the Beyond Zero chief.

ACT minister Simon Corbell, minister for sustainable development in one of the few regions where feed-in tariffs appear to have worked, told the panel his government had put in place an agreement to support 240 MW of renewable energy through a large scale feed-in tariff over a number of years.

Sounds almost German doesn’t it?

For the full discussion download the audio at the Radio National website here.

As you can see it has solar panels on 2 separate roof areas. In solar jargon, you would say there are 2 “strings” of solar panels.

The main string is facing North, which is the best roof orientation for solar panels. These panels should get the optimum amount of sun throughout the day.

The smaller string is facing East. These panels will get 15-20% less sunlight than the panels facing North.

Obviously the installer could not fit all the panels on the North facing roof. Fair enough.

If your home will require solar panels on multiple roof areas, which face different directions, then you must use a special type of inverter to ensure that you still get good system performance.

Multiple Roof Areas Require Multi String Inverters

If you have solar panels facing different directions then you need a Multi String Inverter (also called a Multi MPPT inverter) with one string/MPPT for each roof area.

In order to maximise output from your solar panels, each roof area’s panels must be connected to a separate inverter string that has its own Maximum Power Point Tracker (MPPT). The MPPT is a bit of electronics that optimises the power from the panels. It is impossible for an single MPPT to work properly if it is connected to panels which are facing different directions.

[ For the technically minded people the reason for this is that the IV Curves are different for each roof area because they get a different amount of irradiance from each string of panels. This means there are 2 maximum power points to choose from and an MPPT can only optimise properly to 1 maximum. ]

If you are using a reputable solar company then they will employ a CEC accredited solar designer to individually design each homes solar system, and take stuff like this into account. If you ask to see the design drawing of your solar system they should show you it. For the solar system above, it would look something like the sketch below – notice how it clearly shows each string is wired into its own MPPT in the inverter.

If your system is not designed like this then the string of solar panels with the least sun shining on it at any one time will drag the other panels’ power down to its low power output. This will cripple your power output. If your solar installer cannot provide a diagram like this as part of your quotation (and more importantly as part of your final contract when you are ready to buy) then move quickly on to a more professional firm.

According to the company website, Hyperion have purchased a 127,000 hectare site near the town of Tuckanarra. The site is near mines and an airport and is judged to have a low risk of natural disasters such as earthquakes or cyclones. Chiefly though, the main advantage of the site for the location of a solar tower is the “horizon solar radiation of 2300MJ/m2″ (read huge), according to the company.

The theory behind the solar tower technology sounds simple enough. A flat, large expanse of a greenhouse-like material is spread around the base of a tall tower. When the sun heats the air under the material it rises (remember your science?) and as such has only one place where it can go: the central solar tower (see diagram). The hot air is forced through the narrow space of the tower where it causes a wind which turns a number of turbines inside the tower.

Hyperion points to three key advantages of solar tower technology over other forms of tapping the sun’s energy.

1. No cooling water is needed for the tower’s operation. This is excellent news for the sometimes parched areas where this technology is most effective.

2. Reliability. The company states that the only moving parts to the tower are the turbines and generators.

3. Baseload electricity. An inconvenient truth for the anti-renewable, shock  jock-led narks, the tower has the capacity to deliver electricity for twenty four hours of the day.

Interestingly the technology is not a recent piece of theoretical work straight from the drawing board. It has been in operation in Spain for around seven years. Indeed, according to SolarQuotes Facebook follower Carl Salat, the solar tower was even mooted in Australia in the 1980s!

The Hyperion website states that the WA solar tower isn’t a done deal yet with the company still seeking approval for the project, according to a Jan 31 article in Energy Matters. However if given the green light, construction will commence in 2014 and is expected to last for around two years.

What do you think of solar tower technology? The future or just a flash in the pan? Have your say here or over at our Facebook Page.

In this post I’ll go through the other important numbers that you should look at when comparing solar panels.

The solar panel specification sheet, looks a bit scary at first glance, with lots of curves and about 2 dozen numbers with techno-babble labels. The good news is that only 4 of these numbers actually need to be understood by you – the consumer. The other numbers are for the (CEC accredited) solar designer to use to make sure that he uses the correct panels in the correct wiring configuration with the correct inverter.

The 4 numbers you have to worry about are these:

1) Maximum Power at STC (Pmax)

This is the number that everyone refers to as the “size” of the solar panel. e.g. a 250W solar panel has an “STC maximum power” of 190W. I went on at  great lengths in my previous blog post as to why this number is very optimistic to put it mildly!

2) Module Efficiency

Some solar panel data sheets also list “cell efficiency”. Don’t get module and cell efficiency mixed up! Cell efficiency if the efficiency of the solar cell (the beermat sized black/blue piece of silicon – many of which make up a single panel) in isolation.  Solar Panel efficiency is the efficiency of the panel as a whole and will always be slightly lower than the cell efficiency because of the gaps between individual cells. Most panels should have an efficiency of 13% or more.

Unless you absolutely need to squeeze as many panels as possible onto your roof, then don’t worry too much about this number. I’ve written a whole blog post about why solar panel efficiency isn’t the most important factor and you can read it here.

3) Power Tolerance – This is the range within which a panel manufacturer is saying the module can deviate from its specified STC max power. For example: if you had a -10%/+10% power tolerance on a 200W panel, the actual panels on your roof could have actual max Powers of between 180W and 220W.

These days it is increasingly common to have a 0% negative power tolerance. Which means that the panel will always have a rated STC max power greater than or equal to the specification. I would argue that a 0% negative power tolerance is also a good sign that the panel manufacturer has got a good handle on its quality control and manufacturing processes. So my advice is – be choosy and look for panels with a 0% negative power tolerance.

4) Maximum Power at NOCT

Not all data sheets have this number – but most reputable brands will list it. If it is not listed, that may be a sign of a not-so-great panel manufacturer.

This number is the maximum power of the panel when tested in harsher conditions than the STC max power. It is the power with less sun, and at higher panel temperatures.  It will typically be between 70-75% of the STC power. It is useful because it takes into account how much power is lost due to increasing temperatures.

If you want to quickly get an idea of which panels will give you more power in reality – even though they have the same STC max power – then choosing the panel with the highest NOCT max power should give a fair indication of the best one for the hot Aussie conditions.  It does, of course, depend on the manufacturers’ specs being truthful!

So there you have the 4 numbers that you need to know if you want to compare solar panels before buying. If you think there is a critical spec that I’ve missed out then let rip in the comments.

Does a solar panel with a “Max Power” rated at, say 190W, really produce a maximum power of 190W when it is on your roof in the blazing sun?

Short Answer: Not on your nellie!

The max power rating (in Watts) that your solar panels are rated at is the figure that everyone quotes when talking about “panel size”. If the installer or salesperson talks aout a “190W or 250W panel” they are talking about the “max power” rating of the panels. This rating is based on the power output measured from that panel under “Standard Test Conditions” (STC) that, unfortunately, are a long way from “Real World Operating Conditions”.

Under these STC conditions, the solar panel is subject to a light source (technical term: irradiance) measured at 1000W per square metre. That number probably means nothing to you, so you have to take it from me that 1000W/m² is the equivalent of a strong sun.

That in itself is not a problem, as last time I checked, the sun is pretty bloody strong in most parts of Australia. The problem is, however, that the STC power rating is based on a panel temperature of 25°C.

Think about that for a second. The panel temperature is the temperature that the actual solar panel itself will get to when it is on your roof. This temperature is critical because all solar panels lose efficiency as they heat up.

That means that the solar panel has to be no hotter than 25°C to produce its rated max power. Unfortunately a solar panel on your roof will generally be 20° hotter than the ambient temperature (it’s a big black panel sitting on the roof – it’s gonna get hot!). That means that the ambient temperature for an STC test must be only a rather chilly 5°C.

When was the last time you were in strong sun and the mercury was only at 5°C?

Cowboy Salesman Trap #1: Ask him what ambient temperature the module will produce its rated power at. If he says 25°C, push him out of the door!

So unless you live in a very sunny, cold place, you are never going to get the rated power out of your panels. Sorry about that.

The good news is that you can quickly work out how much power you will get in the real world, if you are brave enough to look at the solar panel’s specification sheet (also known as its data sheet). All reputable solar vendors will provide this as part of the quote.

Cowboy Salesman Trap #2: Kick him out if he can’t or won’t provide a spec sheet for your solar panel that looks something like this:

Here’s how to work out the real max power output of your solar panels from the solar panel specification sheet:

First look for the part of the spec sheet that contains the “Temperature Characteristics”. And look for the both the “Nominal Operating Cell Temperature”(NOCT) and the “Temperature Coefficient of Pmax“. I’ve highlighted them on this spec for a Suntech panel (STP190S-24/Ad+):

The NOCT is the temperature that the panel reached in the lab when subjected to 800W/m² of irradiance (moderate sun) at an ambient temperature of 20°C.  So it’s a much more realistic measure of the temperature that your panels are actually likely to operate at. Here you can see that our panel will get to 45°C.

All solar panels reduce their power as they heat up. The “Temperature Coefficient of Pmax” tells us how much power it loses for every °C that the panel is hotter than 25°C (Remember that 25°C is the panel temperature that the STC power is measured at). The Suntech panel above will lose 0.45% of its max power for every degree above 25.

The NOCT has told us that the panel will typically sit at 45°C so it is a simple sum to work out the power loss at this temperature:

(45°C-25°C) x -0.45%/°C) = 20 x -0.45% = -9%

So expect the real max power out of the panel to be 9% lower than the panel’s rated power. The Suntech STP190S-24/Ad+ is a 190W panel, so I would estimate its real world max power to be approximately 91% x 190W = 172.9W.

This is a much better number to use for solar panel comparison than the STC rated max power, because it takes into account the temperature performance of the panels, which is important Down Under! In fact in the USA the power we have just calculated above is on most solar panel specs and is called the PTC power (which stands for PVUSA Test Conditions). And even better than that, if the panel is approved for use in California, they actually measure the PTC power in a lab so that they don’t have to rely on the manufacturer’s numbers to calculate the PTC power. When they started doing this in 2009 they found that the real numbers were worse than the manufacturer’s claimed specs by an average of 6%.  Check out the comparison tool I’ve put together that lets you compare the PTC of solar panels approved for use in Australia and California, if you need to compare panels before buying.

If you are interested in how the Suntech panel we used for our example tested in the lab, you can see the Californian Test results here. It actually tested to have a PTC of 171.5W, pretty damn close to the 172.9W calculated above. This goes to show how reputable brands like Suntech are gonna give you accurate numbers, but if you are buying your no-name panel from “Dodgy Bros” you might want to take the specifications with a pinch of salt.

I got this email today:

“Hi Finn,

I’ve got a quote for a 1.5kW solar system for $2500 and a 3kW system for  $6000. I want 3kW. Why don’t I just buy 2 x 1.5kW systems???

Cheers, Bob”

Bloody good question Sir!

In fact I can’t believe more people don’t ask this question. But, as always, if something seems too good to be true…

The reason you can’t buy 2 x 1.5kW systems for less that the price of a 3kW system is this:

The full solar rebate only applies to the first 1.5kW of any system, and this rebate is 3x bigger than the rebate for any subsequent kW.

Another way if saying it is that: You get 3 x RECs for the first 1.5kW and the rest of the system only qualifies for 1 x RECs. You can only claim the 3x RECs once.

So the price of the first $2,500 1.5kW system is as follows:

Full price for 1.5kW system:  $5,500

Less Rebate: -$3,000

Cost to you:    $2,500

If you then go and buy a second 1.5kW system, you only get one third of the rebate so, unless you break the law, and double dip, here is what you will pay:

Full price for 1.5kW system:       $5,500

Less Rebate: -$1,000

Cost to you:    $4,500

Total cost for 3kW bought as 2 separate systems = $2,500 + $,4,500 = $7,000

However, if you just buy one 3kW system, you will pay about $6,000, broken down like this:

Full price for 3kW system: $10,000

Less Rebate: -$4,000

Cost to you:    $6,000

So sorry Bob, it is still cheaper to buy the single 3kW system!