Residential Solar Site Measurements: Page 3 of 7

New Developments

“We are now able to sell or lease a system before visiting the house,” comments Mateo Williford, a technologist at Sungevity, a solar lease provider. “Once a system is sold, we do a site visit. It is important that the on-site measurements are accurate so that we can confirm the system that we designed remotely.” Jerry Shafer, CEO of Affinity Energy, a PV and solar heating integrator based in Windsor, California, advocates doing a site visit before selling the system. “There is no substitute for getting your feet on the site and looking for yourself,” he says.

Online Tools for Roof Measurement and Layout

A variety of online tools can help users perform basic and advanced system sizing, array layout and in some cases energy production estimates. These tools give users the ability to make measurements on top of the aerial images.

Clean Power Finance (CPF). CPF Tools is an advanced solar proposal service with a roof measurement tool that characterizes roof shape, dimensions, tilt and azimuth. Additional features enable string sizing, array layout and financial modeling.

Google SketchUp. This online 3D drawing program provides a complete CAD environment, a rich library of images and advanced capabilities for shade visualization. Solar software suppliers have added a variety of capabilities by developing SketchUp plug-ins to enable drawing buildings and obstructions. Examples include Bright Harvest Solar and Skelion. In addition, Google Building Maker enables convenient drawing of a 3D building. (This is currently available in only some locations.)

In My Backyard (IMBY). Developed by the National Renewable Energy Laboratory, IMBY is a solar simulation tool that allows the definition of array area on an ortho image, and then enables basic PV system calculations including energy production modeling.


The widespread availability of aerial images from Google and Bing brings new tools to the solar sales process (see Resources). Integrators can use aerial images to determine approximate roof size and identify any showstoppers before visiting the site. In addition to aerial images, a variety of related services are available to help solar firms prospect, qualify and develop solar opportunities.

“It’s typical for contractors to pull up imagery like Google Earth while on the phone with a client,” states Brian Farhi, vice president of marketing and business development for SolarNexus, a supplier of software for solar business and operations management. “This provides a first pass at whether a roof is suitable,” he continues, “and allows the contractor to ask the customer some targeted questions to rule potential designs in or out. However, an onsite assessment is eventually necessary prior to finalizing any designs, since imagery can be out-of-date or can fail to show all the necessary details.”

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