Evaluating Your Roof for Solar

Determining your roof's suitability for solar panels is a foundational step in transitioning to renewable energy. Collaborating with experienced solar professionals and adhering to local regulations will set you on the path to harnessing the full potential of solar energy, benefiting both you and the planet.

Age and Lifespan
Solar panels gradually lose efficiency, but most are warranted to produce between 86% and 92% of year 1 output in year 25. If your roof is near the end of its lifespan, you will want to replace it before installing solar with a durable material, such as 40-year rated asphalt shingles. This saves having to remove and reinstall panels when the time comes to replace the roof, which currently costs $300 to $500 per panel. If your roof has 12 or more years of life left, you might go ahead and install solar now and spot-fix future roof problems (assuming you still own the structure). Areas covered by solar panels will be largely sheltered from the elements.

Orientation, Solar Access & Shading
Roof orientation and exposure to sunlight are pivotal factors in kWh output. While a south-facing roof maximizes total output, an east-west orientation can still save money now that panel efficiency has become so high, and will produce more energy in the morning and late afternoon. Identify tall trees, neighboring buildings, or other objects that might cast shadows on your roof, reducing total sunlight that panels can capture. While microinverters and power optimizers mitigate the effects of shading somewhat, minimizing shading will optimize energy production and maximize your return on investment. Trim your trees back if necessary.

Roof Material
Your roofing type influences the installation process and cost. The ideal roof from an installer's perspective is newer, asphalt shingle, with a 22° or so pitch. Cement tile or metal can trigger an adder per Watt. Clay tile, shake, and slate roofs are especially tricky, and even declined by some installers, because they lack tensile strength and can break when walked on. Collaborate with a solar installer experienced in working with your specific roof type for a seamless installation process.

Pitch and Tilt
The angle at which your roof is pitched affects panel performance. Ideal solar panel pitch aligns with your specific geographical latitude. This is rarely the case, but advancements in solar panel efficiency make it possible to still produce significant power. Flat roofs, or a roof pitch greater than 30°, are more difficult to install on and may trigger an adder. Flat roofs require a more sophisticated mounting framework and chemical sealing of roof penetrations, but have the advantage of being tilted to a more ideal pitch.

Obstructions and Roof Configuration
A broad swath of unobstructed roof area to accommodate 1-2 large arrays of solar panels is ideal. Complex roof designs, dormers, skylights, and vents can prevent this. Installations requiring many small arrays are more work, and will be a cost adder.

Snow, Critters, and Leaves
Leading solar panels have a high snow-load capacity, and are braced on both long sides by the racking equipment. But if you periodically accumulate four feet or more of heavy snow on your roof, you might opt for a middle brace. Critter guards are metal wire-mesh mounted along the outside of each panel array, preventing squirrels, birds, and leaves from entering under the panels. Extra bracing or critter guards will add to the cost.

Proximity to Your Electrical Panel
Connecting the solar panels to your main service panel is a necessary step. An unusually long conduit run could trigger a small adder. If the best solar access is on the roof of a detached garage behind the house, connecting to the main service panel might require many feet of trenching through concrete. If the garage has an electrical sub panel, connecting there could be preferable, even if it limits where the new solar power will be distributed.

Will My Roof Leak?
On pitched roofs, solar panels sit elevated about four inches for ventilation, attached to a metal racking system. Any competent installer can mount the racking to the roof without creating leaks.