If you look around, you are likely to notice that more and more roofs in your neighborhood are getting filled with solar panels. Which makes sense because all those homes use electricity and the solar panels are going to save those homeowners lots of money. But not every roof is the ideal place for solar so let’s talk about what makes a roof right for solar.
First, the weather where you live will make a difference in your solar output, but even places where it rains a lot like Portland get enough sun for solar to make sense. If you are getting a solar production estimate, it is important that you use the correct zip code so you get an accurate estimate, but any location is going to have enough sun to save you money.
The next thing to look at is the orientation of your roof. Solar panels produce the most power when the sun is hitting them directly. While you may think that north-facing roof looks bright and sunny, the sun never hits it at a direct angle and it is not a great place for solar panels. But sometimes people do install solar on the north facing roof so let’s get into some details on this.
In the continental United States, solar panels facing South at about a 30 – 40 degree tilt angle will produce the most electricity annually. If you are in the southern states, the lower angle is better because the sun is higher in the sky. If you are in the northern states, the steeper tilt angle is better because the sun is lower in the sky.
If your roof is not quite facing due south but it’s close (within 30 degrees of south on a compass), it will still produce almost the full amount of power. If it is facing east or west you will lose about 15% – 20% of the annual production. The steeper the roof is, the more you will lose. So if the roof is pitched 10 degrees to the west, it will only be a 15% loss but if it is at 35 degree pitch to the west it will be more like 20%. A north facing roof will be a 30% – 50% annual loss depending on the pitch.
The pitch also matters on a south-facing roof 30-40 degrees is ideal for annual production and a roof that is totally flat will be at a 10% loss in the southern US and a 15% loss in the northern US.
Now, there are times where annual production is less important and you want to optimize production for certain situations. This will generally depend on your electric rates. The most common example would be if you are on a time of use electric rate and you want to optimize production in the afternoon when the electric rates are the highest, then you want to use that west-facing roof even if it produces less power annually.
Another thing about evaluating the roof is that size does matter. Solar panels are typically 5.5’ x 3.5’ or 6.5’ x 3.5’ so you need to make sure there is room for as many as possible. You also need to leave room based on your local fire codes which often require 3’ at the ridge and one or two 3’ walkways from the eave to the ridge.
Age matters too. If the roof is going to need to be replaced within the next 10 years you should do that before installing the solar. Otherwise, you will have the expensive task of removing the solar to replace the roof and you don’t want to set yourself up for that kind of hassle.
Roof material is also a consideration but there is an attachment for every kind of roof so any roof can get solar installed. It is just that some roof materials, like easily broken clay tiles, are more difficult to deal with while you are installing solar. You will need to think about the extra labor and the cost of replacing the tiles that you break when determining your solar budget.
So, there you have it, you can put solar on almost any roof, it is just that some roofs will provide more solar production and make the installation easier. If you have any questions about your roof, call the experts at GoGreenSolar.com and they will help you navigate the roof evaluation process.