Solar Power
Tilt frames maximise power output, at a price.
Here is (another!) really common question that I get:
“I’ve got 3 quotes for solar: The first company says my roof is at the wrong pitch and wants to charge me hundreds of dollars extra to put my solar panels on tilt frames to optimize the amount of electricity I get. The second mob say it is fine to just put the panels flush on my roof and the third guy says that, yes my roof isn’t at the perfect pitch, but the best solution is to mount them flush to the roof and simply add an extra solar panel to make up for any reduced power output.
Now I’m really confused! Help!”
The problem here is that there are 2 extremes of solar installer in my experience:
At one end of the spectrum you have The Solar Purist. He is only happy if the solar panel is positioned for the absolute optimum power output – he is a perfectionist, highly technical, and has been in the industry since the dawn of solar, when solar panels cost 10 times what they do today. He thinks a few hundred dollars is a small price to pay to squeeze a bit more power out of those precious solar panels. And please, never, ever suggest to him that he uses a non-German inverter. Or feed him after midnight.
Then at the other end of the scale – you’ve got the “She’ll Be Right” Solar Installer. He just wants to get the install done. If you’ve got a roof, and it doesn’t face south and it’s not completely shaded he’ll bang the panels on, and move on to the next job.
I would argue that the best installers for your home are somewhere in the middle. i.e. ones that will give you a safe install that is not “Gold Plated” but will still maximize your return on investment.
In terms of whether to install tilt frames or not – this means that a good solar installer should show the financial consequences for each option and let you decide whether tilt frames are a good investment or not.
So let’s look at a typical scenario where tilt frames would be an option and see which of our 3 original options makes the most sense from an economic perspective:
To Tilt Or Not To Tilt
That is the question. Whether ‘tis nobler to suffer the slings and arrows of the solar purists, or just get the best ROI…
Sorry.
How to work out if tilt frames make sense or not:
Imagine you have a house in Adelaide (lucky you!) with a North facing roof that has a very shallow slope of 10° and you want to install a 3kW system.
The perfect tilt angle for solar panels is the same as the latitude of the install location. Adelaide has a latitude of 34°.
The Clean Energy Council installation guidelines say that the tilt-angle of the solar panels must within 10° of the Latitude. So if we follow those guidelines, we’d have to use tilt frames for our solar panels right?
Panels at the perfect Angle:
If we crunch the numbers with my favorite free, online solar power analysis tool, PV Watts, then we can quickly work out that 3kW of north facing solar panels at the perfect angle of 34° will produce 11.9kWh per day averaged over 1 year. If we value our electricity at 25c per kWh, then that earns us $1088 per year.
Panels at 10°
If we crunch the numbers for 3kW of North facing solar panels at only 10° then we discover that we get 11.4kWh per day which makes us $1041.
How much do tilt frames cost?
Assuming our 3kW system uses 250W panels, the extra cost of tilting 12x250W panels should be around $300.
So to make an extra $47 per year, we are going to be spending $300. About a 6 year payback. Whether you think this is a good investment is completely up to you. But your solar installer should give you the numbers so you can make an informed decision!
I personally wouldn’t bother, mainly because, if you use tilt frames on your roof, you can fit fewer panels on that valuable roof space. Why? Because you need to leave extra space between the panels so that one row of panels doesn’t cast a shadow on the row behind it. I also think that tilt frames are butt-ugly. But perhaps that is just me.
What about adding an extra panel?
The third option you have – is to make up for any lost power by simply adding an extra solar panel. A few years ago, when panels were 5x the price, this would have been an insane suggestion (and some old school solar installers still think it is a terrible waste!). But in 2012 it can make a lot of sense.
The cost of one extra 250W panel will be about $400. Installed flush to our roof, this 13 panel system will generate 12.36kWh per day and make us $1128 per year. So your extra $400 investment is returning you an extra $169 per year compared to the 12 panel system at 10°. And an extra $128 compared to the 12 panel system mounted on tilt-frames at 34°.
I’d say that the extra panel is a much better investment that the racking. The third installer was right!
Note: One thing that you don’t want is completely flat panels (angle = 0°). You want them to slope at least 10° so that the rain flows down the slope and helps the panels self clean.
Are you a fan of tilt frames for solar panels? Then let rip in the comments below!
About Finn Peacock
My retailer has tried to charge me $800 to upgrade my smart meter to take the TFIT tariff and connect me to the grid. When I argued the cost I checked with PowerCor and they quoted $238 to change the meter and $32 to reconfigure it. I am now in my third month waiting for the upgrade and connection to the grid. The next argument will be wether I am going to be compensated for the solar credits on the meter.
I have now been charged over $450 for the meter upgrade and I have not had the meter upgrade or connection to the grid. The impersonal continual threats to disconnect me via voice actuated smsing is ridiculous.
AGL customer service is located in Malaysia or somewhere similar. The girls are nice but with the amount of problems I have had and the average call duration of one hour being passed from department to department is absolutely absurd.
find another retailer.
Excellent article and very true. However I think you under estimated the cost of tilt framing a 3.0kw system. The whole price for a decent tilt kit(one which comes with an engineering report ) would be almost $300 and then there is the extra time to install it properly. Nothing worse than seeing an ugly tilt frame system or the panels all stressed and twisted. Then thee also time for council approvals(This can be a pain in the but with some councils) Most installers would charge $800-$1000 extra to tilt frame a 3.0kw system
This extra cost for the tilt frames is more reason not to waste your money on them and go up 1.2 x inverter output (can still get stc rebate for the extra panels)with extra panels
Therefore my opinion is no to the tilt frames.
Thanks again for your comments. I just have one final question (i think). I have noticed that on cloudy days my inverter is producing lets say 1.5kW. When the sun comes out, this will increase rapidly to approx 3.5kW. If the sun stays out, the production will slowly reduce and settle around 3.1kW. can you tell me why this happens?
yes – solar panel efficiency decreases with temperature:
http://www.solarquotes.com.au/blog/the-truth-about-solar-panel-performance-and-temperature/
Hi Finn,
Your articles and commentary on solar panel efficiency are very enlightening and your web site is a great resource for solar panellists.
I had 16 x 245W rated panels installed in July 2012. they are arranged in a straight line across a northern roof at about 25 deg pitch in Brisbane. The output should be up to 3920W but I have seen the output beyond that ‘maximum’ and over 4100W.
Is this due to clouds passing across the sun – cooling the panels – then moving away allowing the sun to shine on cooler panels with resulting short term spikes in output?
If this is correct, then warm days with intermittent clouds could potentially produce more power from the panels in comparison to a continuous warm and clear day. Do you have an comment re this?
Many thanks
This has a few names, Lensing, Edge effect or just cloud effect. Just the clouds reflecting more light than normal sunlight
Hi, Finn. First, many thanks for an informative site. I’ve now used PVWATTS to model my potential installation options on a system yet to be installed, neither of which are north facing (due to shade issues). Noting your firm views on south angled panels, I thought I’d offer my results for interest. My roof space and shade limited options are either East azimuth at an average 30degrees (3 panels@25deg plus 4@33deg) or (horror) South azimuth at 9.5deg. PVWATTS actually generates a very similar average annual output (~2.3MWh for 1750W Pmax, in Perth WA) for both scenarios. The optimal 32 deg North az. option would yield ~2.7MWh (17% more). The East facing install is slightly better in winter and, obviously, peaks in late-morning. The South facing slightly better in summer and peaks around midday. I plan on opting for the South facing as it has the simpler install (one group of 7 panels) and minimal risk of shade developing over time as trees grow slightly. I had originally considered tilt frames on the South roof, but at $480, it was more cost effective (and prettier!) to add a $300 panel instead. Can you offer an opinion if you think I’ve overlooked some angle (sorry) on this? Thanks, Andrew
Hi Andrew,
Now solar panels are so cheap relative to a few years ago South pacing panels can make sense in Australia. Especially if you have a very small roof pitch like yours.
PVWatts is pretty accurate – and you’ve done exactly the right thing. Quantified the energy yield before deciding where to stick the panels – I wish everyone was so scientific in their approach instead of the wild assed guesses you often see.
AT the end of the day a South facing solar panel in Australia will still give you more power that a perfectly oriented panel in Germany!
Finn
Hi Finn,
Cheers for that feedback. I’ve now used your online cost calculator – very neat – and confirmed my own estimates were in the ball-park of a 5yr ROI (at 55% export) at the likely yield. Encouraging!
Other links on the site have led me to NASA’s irradiance data, and I’m pretty amazed to find we get ~950W/m2 peak in January here in Perth. As you say, wouldn’t happen in Germany! And means I won’t kill the proposed 1.5KW inverter (1800W Pin max) with 7x250W (Pmax) panels.
Once again, thanks for your comprehensive site. I don’t know where you find the time but I hope it pays you.
Cheers, Andrew (also an Engineer, which may explain the approach!)