Building entirely new roof, how to find best angle(s) for solar?

[Jeremiah]

The roof of the house we bought is totally shot, it all must be totally rebuilt (rafters and all).

So I'm thinking to just make a flat roof tilted at a certain angle or angles to optimize our solar production.
We'll make it generally South facing and the builder said he can do about a 20 deg. angle (he balked at 15 deg.)
So I was thinking about it and wondering if a secondary angle would be beneficial since it's all being rebuilt from scratch anyway.
If so, does anyone know of any tools to calculate the best stationary angles for 2 axis?

We live fairly close to the equator and there are some trees to our West we cannot cut down (effects later afternoon shading) so I'm also wondering if there could be some sense to tilt the roof a bit toward the East...
The house orientation now has the Southern exposure at South but slightly facing East (9 deg)

*** edit ***
The rainy season is here June-November, would it make sense to just focus on the best average angles for that season? I'm wondering if the diffusion of light in the rain will make optimal angles less important?

Using this tool: https://solarsena.com/solar-panel-orientation-calculator/
It says part of the year the best orientation is South but part of the year it's North and Northwest.

 

[pollenface]

If you have an Android phone. Download "Optimal tilt for PV systems"

It will give the best angles based on your gps location. It also allows your phone to be used as an inclometer when mounting panels.

 

[littleharbor2]

Another great app is "Solar Tilt". Very flexible and has GPS and a tilt gauge built in

 

[OffGridForGood]

Another great app is "Solar Tilt". Very flexible and has GPS and a tilt gauge built in

I don't think those apps work for Mars...OP listed location.

 

[Jeremiah]

I don't think those apps work for Mars...OP listed location.

true, no gps constellations yet

 

[ColoradoRider]

The roof of the house we bought is totally shot, it all must be totally rebuilt (rafters and all).

Have you considered going with a ground mount?

 

[Jeremiah]

Have you considered going with a ground mount?

we don't have that much space on the lot; entire lot is like 250 sq. meters, much of that is occupied by the house. Probably will build a carport using bifacials though.

 

[MichaelK]

For my own location, with a shed-roof with only a 5% angle, I built a array frame out of unistrut members at the best angle to the sun. I have metal roofing though, so it was realitively easy to bolt the array frame down on the roof.

 

[gotbeans]

Solar Irradiance Calculator

www.solarelectricityhandbook.com

this will say the optimal angle for all seasons and then the yearly optimal angle

 

[hwy17]

You can model all the inclinations on pvwatts. The boring part is that it doesn't make that big a difference, orientation does.