If you live in Australia, you get your passive solar gain by facing your house to the North...

It also depends on whether or not you have obstructions to the east or the west.  From a PV solar gain standpoint, the shading that I cannot avoid from neighboring property on the west limits the solar gain in the evenings.  For the maximum possible output of my PV panels, considering I get limited western exposure, I "might" come out better for PV purposes by angling my house so that it faces a little more southeast to get the maximum "available" exposure.

However, from a passive solar standpoint, you want to avoid the sun rising low from the east and setting low in the west; you want to have limited windows on the north, and you want a south facing exposure (in the northern hemisphere), to get passive solar heat gain in the winter, and with eaves designed to block the higher summer sun.  It pretty much takes smart design with a north/south orientation to accomplish this.

In my case, if I were to angle my house southeast to capture more available sun to my PV panels, then I wouldn't be capable of maximizing the passive solar design of the house.

For me, the passive solar side of the design is my priority so I am going to face the rear of my house due south.  There are alternatives to direct roof mount systems that can help me achieve preferred angles for PV panels, if I so choose.  There is little substitute for a southern exposure in passive solar design.

My planned home is in Northeast Alabama.  From your comment I'm a bit confused.  I've always heard that for passive solar design a due south orientation is optimal.  But when maximum solar gain isn't possible or perhaps not desirable, I can sort of see your point.

I've limited the amount of glazing on the west of my house and the harsh afternoon sun is blocked by a rising hillside (my 1st floor will be at the elevation of my neighbor's basement garage door) with 3 story houses on it.  So I don't need to angle my house to the southeast to avoid the harsher afternoon sun.  Additionally, there is a steeply rising, high peak east of my house (a very nice view; the steep rise starts on the other side of the adjacent 40 acre undeveloped property) that blocks the early morning sun from making it under the wrap-around porch.

I'm using a wrap-around porch to shade my home in the summer.  The south facing porch is designed to be enclosed as a solarium in the winter for maximum passive solar gain, and functions as a screened in porch during the rest of the year.  This home design appears to be fairly optimal for a passive solar design.

HOWEVER... I'm intrigued by your comment that a home where cooling is more of a factor can actually benefit from facing slighly east of south. 

My neighbors' houses on my side of the street are also oriented due south.  But the street at my lot begins to curve to the northeast and my best views are to the northeast and the east.  Most critically, by facing my house due south, I am struggling with a prospective set-back requirement problem on my home's northwest corner that is difficult to stay within without the removal of a VERY old and beautiful sourwood tree to the south of the planned house site. 

If I were to angle my house to the southeast, I would actually have better views, I would align the front of my house more appropriately with the street curb and also with the house across the street from me, I would have prospective better cumulative PV solar exposure (due to my shaded western exposure created by the high hill and due to the tall neighboring houses to the west), I would easily resolve the set-back issues on my northwest corner without risking the sourwood tree, AND my swimming pool would be less visible from the neighbor's house!  Additionally, more of the rear of the basement would become "walk-out" accessible.

The primary downside I can think of is that with a due south orientation, my front door aligns very well with a clearing that extends to the street for a nice "curb appeal" view of the house without taking out many trees.  With a counterclockwise rotation of my plans to make the house slightly east of south facing, the front of the house would actually end up facing a relatively dense grove of trees that I'd rather leave in place.  (With the planned southern orientation, the grove makes for a private lawn area in the northwest of the front yard.) 

In particular, there is a GIANT ~ 8 foot tall huckleberry bush (more like a tree with its 10" diameter trunk) within that cluster of trees that would almost certainly have to be removed for curb appeal (with the house sloping rear-ward, this dense 8 foot tall bush would obscure the view of the front door from the street).  I'd really like to save this abnormally large huckleberry TREE, with its cinnamon colored and architecturally interesting trunk and limbs.  While most would consider a huckleberry bush as anything but a landscape plant, they are good for the native wildlife, and this one is particularly interesting...  In all my years of hiking through forests in Alabama, this is the biggest huckleberry bush I have ever encountered.

With the rotation of the house plan, I would also lose the planned view of the sourwood tree cluster from the breakfast nook.  And the resulting angles of the backyard would drastically increase the size of the required deck off of the south porch (to level a significantly sloped area without impacting the roots of the sourwood trees).

From talking with passive solar homeowners during the ASES Solar Home tour this month, winter heating is not much of an issue around here with the passive solar gain of a south facing home, even though we actually have more heating degree days in Alabama than cooling degree days.  By angling the house to the southeast, I would probably warm my house a little earlier in the morning during the winter, which would also be a good thing...

Your comment makes me think I really should be considering angling my house slightly east of due south!  This may be possible if I can simultaneously shift the house eastward (encroaching on my second lot) without taking out the large cluster of maple trees that are currently positioned in front of the northeast corner of my house.  That way my home could be positioned to be able to still leave the huckleberry tree in place.

This is a major paradigm shift for me...  Any thoughts?

While a southeastern orientation may have been acceptable from a passive solar standpoint, it won't work with my trees.

I went into my house plans and rotated my house to the southeast to align with the street curb.  It actually made my set-back issues worse!  I'd either have to lose the sourwood or lose the cluster of mature maple trees and I'd still wind up losing the huckleberry tree.

With the due south orientation, I can likely keep every tree while staying within the set-back, only risking trauma to the sourwood.

I'll be sticking with the due south orientation.  I've already controlled the summer exposure with the house design, and a due south orientation certainly won't hurt my solar goals.