Solar 101: Is my roof right for solar?
1.8 kW solar power system, Philadelphia PA
If you’re looking into solar, you’ve probably concluded that you’re going to need a South facing roof. You may also be thinking that your heavily pitched roof just won’t cut it for solar. But, don’t give up on the Solar dream just yet!
You may be surprised to know that many solar systems are not installed on a perfectly South facing roof. Nor are they mounted on a 39 degree roof. Although these attributes would make for an extremely efficient solar system, you should not discount yourself from the solar market just because your roof does not fit this criteria.
As we mentioned in our previous Solar 101, How the output of a solar system is calculated, orientation (north, south) and pitch (angle of your roof) are factors that influence the performance of your system – but just how much?
Orientation
The orientation of your system is the direction that it faces (e.g. South, West, East), which determines the time of day in which your system is directly facing the sun. If your system is installed on an East facing roof, your system will pick up all the morning sun, some of the afternoon sun, and be relatively ineffective in the ladder part of the day. However, if your system faces South, it is able to generate electricity all day, with it’s peak at around 12-2pm, depending on the time of year. But, does this mean that your East (or West) facing roof is not suitable for solar? Let’s find out, using an example:
System Size: 5kW (DC)
Pitch: 30 degrees
Daily kWh (AC) South facing: 18.21
Daily kWh (AC) East facing: 15.32
Daily kWh (AC) West facing: 14.60
As you can see, although a South facing is more efficient (thus, the more preferred orientation for solar), it is not by as much as you may think. So, if your South facing roof is not suitable for solar (shade, obstructions, little space), your East and West facing roofs are still great alternatives!
Pitch
The pitch of your system refers to its longitudinal angle. For example, if your system is pitched at 0 degrees, it would be laying flat; if it was pitched at 39 degrees, it would be directly facing the sun during summer. As most residential systems are installed on a pre-existing roof, the pitch of the system cannot be altered; it is equal to that of your roof. So is the pitch of your roof right for solar? Let’s find out, using another example:
System Size: 5kW (DC)
Orientation: South
Daily kWh (AC) 0 degree pitch: 15.70
Daily kWh (AC) 20 degree pitch: 17.92
Daily kWh (AC) 39 degree pitch: 18.31
Like with orientation, we can see that even the typically less-desireable roofs are still solar-friendly.
So before you count yourself out of the Solar game, allow a Solar professional to assess your roof first – you may be surprised at the results!
Data obtained from http://rredc.nrel.gov/solar/calculators/PVWATTS/version1. Location: Philadelphia.