Cities are rolling out solar maps to let residents see who in their community has a solar installation and also learn about how much energy could be harnessed if their roof were decked out in solar panels.

The San Francisco Department of the Environment launched the San Francisco Solar Map after the city set a lofty goal: to have 10,000 roofs equipped with solar power by 2012. The current count is 871. The solar map's goal is to offer residents and business owners a simple tool to learn about solar installation.

"We wanted something that would help people in San Francisco, that would break down some myths about installing solar in San Francisco, and then offer a tool to people who were interested in solar but didn't really know how to take the first step," said Johanna Partin, renewable energy program manager of the Department of the Environment.

The city presented the idea to engineering firm CH2M HILL in spring 2007. According to Ryan Miller, lead technologist for solar mapping initiatives for CH2M HILL, the solar map combines aerial photography, GIS software and client-supplied data, such as parcel maps and information from the tax assessor's database.

There are two aspects to the solar map: mapping existing solar installations and providing information for residents and business owners who are interested in installing solar panels.

Existing solar installations data points are mapped through the portal, incorporating characteristics of each installation, including system size, the amount of electricity it generates, the installer, a link to the installers' Web site, and an opportunity for the home or business owner to post photos and quotes. This information is displayed after users click on a dot on the map that represents each location where photovoltaic systems are installed.

For citizens interested in solar there's the option to type their address into the Web site and the technology identifies shading obstacles on the roof, such as HVAC units, skylights, perimeter walls or a taller building that could block sunlight, said Dave Hermann, client solutions director of CH2M HILL.

"It takes out the unusable space," Partin said. "It takes out the kind of north-facing side of the roof, if it's a pitch roof. It takes out the shaded areas; it takes out roof obstructions and those kinds of things."

The site estimates the amount of carbon dioxide that would be reduced, power output and system cost and size.

San Francisco uses Google Maps as the platform, but CH2M HILL said it is also able to create maps using Microsoft Virtual Earth and is working on implementations using ESRI solutions.

San Francisco hasn't yet received feedback from citizens that the solar map directly led to solar installation, Partin said, but the department has heard that potential customers use information garnered from the site when speaking with solar installers. She suspected the main driver is city grants for residents who install solar power.

The complete article will be published in the January 2009 issue of Government Technology.

Elaine Rundle  |  Staff Writer