Installation on a flat roof
It is recommended that solar panels are mounted at a 10-15 degree angle on flat roofs. This is mainly so rainwater can flow off the panels instead of sitting stagnant on top. If panel installation with a 10-15 degree tilt is not desirable or practical the alternative is an increased frequency in cleaning and servicing so that any build up of dirt does not get a chance to become too large.
Roof pitch during winter
Another general rule is to add 15 degrees to the latitude angle of your home so that your solar panels are more efficient during winter. This is more useful in sunny states like Queensland where you may want to install solar panels with winter in mind rather than summer.
This decision still depends on other factors like roof orientation and type, and your solar energy goals. Read our post: Make the Most of Your Solar Panels with These 5 Tips, for more information.
Summary
Roof pitch is the slope of your roof. The ideal angle for your solar panels largely depends on your location and the weather in your area, but generally, in Brisbane and Gold Coast, a roof pitch of about 27-28 degrees is ideal.
To make the most out of your solar energy system during winter, you should request an extra 15 degrees to the latitude of your area. You should also keep in mind your solar energy goal, roof type and roof orientation before requesting this.