Good day

I know that the hours daylight has an effect on the total power generated. The angle of the sun of course also has an effect on the peak power that can be generated. My solar panels are at a fixed angle of about 25°. According to my results and calculations the peak power in winter is about 33% less than in summer. 

Please comment on the above, if most of you also have the same result or not.

Hi Ridiq

Plugging in an estimated Lat/Longitude for Centurion into my solar calculator program gives the following. This assumes that the panels are oriented directly North.

The Blue curve is the kWh available for a "perfect" tracking 1kW panel (i.e. always pointing directly at the sun). The orange curve is for the fixed 1kW panel.

Edited June 19, 20196 yr by NigelL

You are probably right with your calculations. To counteract this I have two arrays on my roof. One at around 45 degrees to best utilize winter sun and one at around 25 degrees for summer sun. It works at peak almost all year round. If I go with a third array in the future it would be set at 33 degrees for mid year sun. 

For most customers, I recommend going for around 45 degrees for a single array as we have the least hours of sunshine during winter, so it makes sense to angle the panels toward the winter sun. These customers generally have a drop of around 25% in summer, but with so many daylight hours it makes up for the loss. It evens itself out with less hours of higher production in winter and more hours of lower production in summer. 

Thanks for the feedback gentlemen, much appreciated.

The advise I have found on other sites regarding the angle at the top of your panel should be based on your latitude.  For mid summer tilt it up 15 deg from your deg latitude and for mid  winter tilt it down 15 deg from your deg latitude.  This really feasable if your panels are on an array rack on a pole or if you do have adjustable tilt panel racks on your roof.

Thank you all for an interesting discussion here. I had my panels installed resting on the roof. What's the pitch of the roof? IDK. Or I didn't until about 5 minutes ago.

I have two arrays, each one being 6 X 3.25 kw Risen panels. The North-ish array is 27deg to the horizontal and faces NNWish - 322 degrees. The 2nd array is sort of ENE. 52 degrees and tilted 30 to the horizontal.

I'm in Blairgowrie, so about 26 Deg south.

So that lot should do better in summer (it's doing OK in the winter). 

So now I am keen on software that is going to give me an idea of the power I can expect. I started with Solcast, but I'm not  sure about all the information it wants (like the effiicency factor). And I'm guessing I have to register the two arrays separately and somehow aggregate the data.

Any advice on a website or piece of software to use?.