Two faces, not twice the guaranteed output
Bifacial describes a panel that can generate electricity from light on its front and rear faces. It does not mean output automatically doubles. The amount of useful light reaching each side depends on orientation, shade, nearby surfaces and the roof. Bifaciality describes rear-side performance relative to the front under comparable test conditions; it is not a roof-specific energy forecast.
A vertical panel stands upright instead of tilting toward the sky. In an east-west-facing layout, one face receives morning sunlight and the other receives afternoon sunlight. Discuss the face directions explicitly with the designer, because descriptions of row orientation can otherwise be ambiguous. The relevant question is which direction each collecting surface faces.
Why the daily curve changes
An east-facing surface receives favorable direct light earlier in the day, while a west-facing surface receives it later. Vertical east-west faces therefore tend to produce two daily peaks instead of the main midday peak associated with a south-facing tilted array. Clouds, seasonal sun angles and local obstructions change the actual curve. This is a characteristic of the geometry, not a guaranteed daily pattern.
A building that uses electricity in the morning and late afternoon may find that profile useful. It still needs a comparison between estimated production and actual demand. A different curve does not automatically mean more annual energy or lower bills. Ask for a layout and yield report that considers the roof and for a billing review based on the utility’s actual rules.
Roof reflectance matters
Albedo is the fraction of incoming light reflected by a surface. A light-colored roof can send more reflected light toward panel faces than a dark roof. The useful reflected contribution also depends on panel height, spacing, weather and surface condition. Roof reflectance is one input to a yield estimate, not a substitute for one.
Do not assume a roof remains equally reflective for its whole life. Dirt, aging and changes in the surface can affect it. The design team should record the membrane type and condition rather than estimating from a distant photograph. Vegetation also changes the light environment, so green-roof projects need their own assumptions.
Snow, dust and space between rows
Snow and dust are less likely to settle on upright glass than on a shallow tilted surface, and snow can slide off. That does not make the entire roof maintenance-free or guarantee clear panels after every storm. Snow around support feet, drainage and roof access still need attention. Inspect the installation according to the supplier’s instructions.
Rows need spacing to reduce shading between panels and to preserve access. That generally means lower installed capacity per square foot than a closely arranged conventional array. A comparison should distinguish installed kWp from specific yield, which is energy per unit of installed power over a stated period. More energy per kWp does not necessarily mean more energy from the whole roof.
Where the layout fits
Where it is not the best fit: on an open flat roof with no weight limit, conventional tilted solar usually costs less and fits more capacity into the same area. Over Easy is for flat roofs only, with a slope of 5 degrees or less.
The reasons to consider it include weight limits, green-roof vegetation and access around equipment. Over Easy units arrive pre-assembled and rest on support feet without roof penetrations. Wind load is calculated per project to establish the layout and whether ballast is needed. ArcEdge supplies the system and supports the roofer or solar installer; electrical connection is done by a licensed electrician.
Frequently asked questions
Does bifacial mean double the energy?
No. Rear-side light depends on the site and layout, so energy must be estimated for the project.
Is the system for pitched roofs?
No. Over Easy is for flat roofs with a slope of 5 degrees or less.