Our solar experts at Merlyn Power want you to get the most power out of your solar PV system, and to keep your maintenance costs as low as possible. That way, you get the best return on your investment while doing the most to protect the environment. If your roof shingles are in poor condition, or close to the end of your life, it’s worth considering a new roof before we install your solar arrays so you can avoid the cost of having the whole system removed and then reinstalled. Many of our customers plan their solar installation to come after a new roof is installed. If you’re in this situation, consider choosing a light coloured shingle or steel roof to improve the efficiency of your home and your new solar panels!
Cool roofs make cool cities
People have known for a long time that light-coloured roof shingles can help to keep buildings cooler and save on energy costs. Light coloured roofs have high solar reflectance (aka albedo). The U.S. Department of Energy calls these “Cool Roofs”. According to the DOE, roof temperatures can reach up to 65 degrees C on a hot sunny day. In the exact same conditions, a reflective roof can be as much as 28 degrees C cooler. That translates to a savings of 7-15% on air conditioning costs or in non air-conditioned buildings reducing temperature by 1.2-3.3 degrees C. It also reduces the temperature around the building! In the evening, the air temperature in cities can be as much as 12 degrees C higher than surrounding rural areas because of heat trapped and stored in pavement, concrete and dark coloured buildings. Installing a highly reflective roof can mitigate this effect and keep your whole neighbourhood cool.
Cool solar panels make more power
If all that isn’t enough to convince you, there’s another big benefit to a light coloured roof. Solar panels are most efficient when they are cool. For every degree C your panels rise over 25 degrees C, you could experience a loss in efficiency of 0.38%. That might not seem like much, but if your panels reach a temperature of 65 degrees C, like a dark asphalt roof can, you will see your efficiency drop by 15%! A highly reflective roof will stay cooler and keep your panels working at their highest efficiency.
The future is bi-facial
More and more solar PV manufactures are switching to Bi-facial panel designs because of their improved efficiency. These panels collect light from both the front and the back of the module. A typical residential PV array is installed parallel to the roof surface with an air gap to allow the panels to cool. Black or dark coloured shingles don’t reflect any light underneath the array. A highly reflective roof will bounce the light up underneath your panels making you more power. It’s a small effect, but with solar every little bit counts.