“Is my roof suitable for a solar installation?” This is one of the most common queries we deal with at Unconquered Sun. It should be said that there really aren’t any deal breaking rooftops out there. Yes believe it or not – the sun also shines in the north and the east just as it does in the south and the west! And most trees shed their leaves in the winter time etcetera, you get the picture… Really, as long a you work with a reputable solar provider when navigating the design of your project, you should have no problem with the analysis. Also, keep in mind most production issues can be overcome with good engineering and the proper application of componentry and technology. Always remember that your main goal should be that the overall production from the solar system satisfies your consumption needs at the property.
Some quick math;
One square kilometer = one million square meters. And one kilowatt per meter of solar radiation hits the planet in many areas of North America daily. Therefore 1 square kilometer (in these areas) receives a gigawatt of solar energy daily!! Soooo, a few square kilometers properly harnessed could power North America. Read more on this subject @ The Ultimate Solar Guide Solar efficiency vs competing fuels edition.
No question that we receive plenty of useful energy from the sun everywhere on the planet! The real question is how to optimize your rooftop solar installation to best harvest this energy and your maximize production depending on your location and the architecture of your home.
Looking for the easy button here? Simply fill out this form and Unconquered Sun Solar Technologies Inc will produce an instant custom design tailored to your rooftop along with a quote for the installation. This analysis will show you exactly what your specific rooftop potential is in terms of solar generated electricity production. However, odds are, if you’ve read this far you are old school and have a quest for knowledge! So let’s explore..
There are certain general factors that apply to any potential solar design:
There are of course, many other contributors to the overall production of rooftop solar. Such as exactly what technology you choose, availability of materials, local by-laws, etc but these are mostly insignificant in comparison to the big 4 listed above.
Rooftop solar latitude
Simply put; the closer you are to the equator, (luck you) the more sunshine you enjoy! and therefore the more energy your solar system should theoretically generate. See the map below published by the world bank which illustrates horizontal irradiation across the entire globe, you can see that in general – the further away you are located from the equator, the less potential energy you receive from the sun.
Unconquered Sun Solar Technologies Inc is a proud Canadian company and therefore our experience and the information published in this article will be focused on locations within Canada. As you can see below from the north american map published by solargis; despite our snowy reputation Canadians still enjoy VERY good solar potential!, particularly in the prairies and south-west Ontario.
These maps show horizontal irradiation, (that is the amount of solar irradiation you would receive if you laid your solar panels flat). However, the benefits from the sun increase exponentially as you increase the pitch (or angle) of the panels! see roof pitch below..
Rooftop solar azimuth
Azimuth is the direction that the roof (and therefore the solar panels) face. In the solar industry this is most often represented as the number of degrees from true-south a roof face is pointed. For example a roof that faces perfectly south would be said to have an azimuth of 0 degrees, while one facing perfectly east or west would have an azimuth of 90 degrees.
In other industries 0-degrees is sometimes north, or even east, so it important to always refer to your azimuth as “x degrees east/west from south” to ensure there is no confusion.
For nearly all roofs in the northern hemisphere, it is optimal to have an azimuth as close to true-south as possible. This is because of the sun’s rising and setting positions and times throughout the year. For example see below the sunrise and sunset times and azimuths for USST’s location in southern Ontario and each of the four seasonal equinoxes:
I.e. sunrise and sunset times & azimuth @ Unconquered Sun’s Location
|Date||Sunrise Time||Sunrise Azimuth||Sunset Time||Sunset Azimuth|
|March 21st||7:35 AM||91 Degrees East of True-South||7:44 PM||91 Degrees West of True-South|
|June 21st||5:55 AM||114 Degrees East of True-South||9:12 PM||114 Degrees West of True-South|
|September 21st||7:35 AM||91 Degrees East of True-South||7:44 PM||91 Degrees West of True-South|
|December 21st||7:57 AM||68 Degrees East of True-South||5:02 PM||68 Degrees West of True-South|
This graphic illustrates the same information:
As you can see, the further away your roof points from true-south the less often it will be directly in one of these “sun-arcs” and the less potential there is for solar energy. However these sun-arcs are different for every latitude, so it’s important that your solar designer is using the proper information for your location, something that Unconquered Sun does automatically for all of our designs.
It is important to remember that the difference in the sun’s position isn’t simply horizontal, the sun also moves vertically (actually the sun stays stationary, it appears to move as a result of earth’s off-axis tilt). See the below image from practical physics for an example of how the sun’s position changes over the course of a year within the northern hemisphere.
Is west or east facing rooftop better for solar?
So south is better than north, but what about east vs west?
There is no practical difference in generation from having a roof in the east vs having a roof in the west, assuming all other variables are also identical. To prove this we can look at one of our (Unconquered Sun) installations in southern Ontario that has a nearly perfect east-west roof, with our solar system evenly split across both roofs and with little to no shading or other variables to consider:
Taking advantage of the precision from the remote monitoring system we have incorporated into this project we can record the individual amount each panel has produced over the span of nearly 3 years:
If you were to add up all the west-facing panels their production would be: 14,441 kWh
If you were to add up all the east-facing panels their production would be: 14,358 kWh
This is a difference of just 1.51%, well within the margin-of-error.
Rooftop solar pitch
Another physical characteristic that will impact the production from your solar system is your roof pitch (the angle of your roof). For instance if your home was located on the equator you would want your panels lying perfectly flat however the further away from the equator you are, the steeper you want your solar panels and your roof to be, if they are facing south. However for roofs not facing south; the shallower the pitch (or angle) the better.
For trackers (mechanized solar systems that rotate to follow the sun throughout the year) and adjustable tilt ground-mount systems there are generally two fixed pitches employed, one for the summer and one for the winter. However, i am devoting the lion’s share of this article to the far more common fixed roof solar system, which has no moving parts.
Roof pitch is measured in construction as the number of inches a roof rises per 12 inches of linear distance. For example 4/12 Pitch means the roof rises 4″ for every 12″ of length. 4/12 Pitch would be 18.43 degrees. Some companies and software will use the construction terminology while others will use degree terminology.
Some common roof pitches for roof tops are:
- Flat-Roof (0-3 degrees) – in this case special racking is used to give the panels an artificial pitch
- 4/12 Pitch (18.43 degrees) is most common among pole-barns and detached garages
- 6/12 Pitch (26.57 degrees) is a very common roof for new-construction houses
- 10/12 Pitch (39.81 degrees) is a pitch commonly found in older “war-time” houses
Which roof pitch (angle) is best for solar?
In our part of the world the best single roof-face for solar would be a roof pointing perfectly south with a pitch of 10/12 or 39.81 degrees. The further north you go in Canada, the steeper that ideal-south pitch will be. It is important to remember that for roofs not pointed south, the shallower the better.
Using the information that we’ve covered on latitude, azimuth and pitch it is possible to build a chart (see below). This chart illustrates the relative solar generation values for roof tops located in USST’s backyard of sunny southern Ontario (latitude). This chart includes any combination of direction (azimuth) and angel (pitch):
As you can see, even the worst-case scenario on this graph still maintains half the solar generation of the ideal situation. So no matter what your azimuth and pitch, your roof will generate solar energy, it’s just a question of how much. If your goal is to eliminate your electricity costs with solar it’s never a question of “if” it’s possible, but instead “how much” solar may be required.
Rooftop solar shading
Shading is anything that can cast a shadow on the solar panels, thus decreasing their generation. Depending on the technology being used in your solar system shading a solar panel could result in that single panel under-performing, a group of panels under-performing, or the entire system under-performing. So it is important to point out and discuss any potential shading with your solar provider.
There are many different shading sources that can be identified and accounted for when designing and installing the solar system, such as:
- Chimneys: static, easy to see and account for in design. However if they are a problem many chimneys can be removed, a service that a good solar provider should be able to arrange.
- Tall sections of buildings or neighboring buildings: static, easy to see and account for in design.
- Heating, ventilation and air conditioning (HVAC) units: on flat-roofs large HVAC units not only take up valuable roof space, but can cast a sizable shadow depending on their size.
- Antennas and satellite dishes: These can be hard to see on aerial imagery, but most often they can be identified and relocated without any major issue. Thanks to the rising popularity of IPTV many of our clients don’t actually use their antennas and satellite Dishes and make arrangements for us to remove them as part of our installation.
- Trees: Not a deal breaker!!! In fact many trees have leaves that die and fall off in the winter , this combined will cooler temperatures can make for excellent solar production during the winter months. If you need your trees trimmed to optimize your solar installation, a good solar provider will arrange this for you.
Ready for the easy button?
So….., If you have made it this far, and you are curious about your rooftop’s potential but you’d prefer to skip the physics exercise above…. NO WORRIES! Let’s get started;
Simply click the links below!
- Request a FREE solar analysis, design and quote
- Pre approve yourself for USST’s exclusive No Money Down, 1.9% un secured financing option!
Well, this concludes the Is my home suitable for rooftop solar? edition of the Ultimate Solar Guide from Unconquered Sun!
Hopefully the above will serve as a valuable reference on your solar journey. I truly hope you have found the content helpful. Please feel free to respond with any comments or suggestions you may have!
More to come!!