As solar power continues to break record after record in both efficiency and price tags, rooftop becomes ever more attractive to businesses and the online tools for solar audits mushroom quickly.

These clever pieces of software turn a few clicks of the mouse into a detailed report to show you whether or not installing solar panels on your roof makes sense for you.

Let’s take a look at some of the most popular new online offerings.



Search engine Google is a name that sticks out as the giant rolled out in August a new application for calculating a roof’s solar energy potential. The application is currently free of charge, but only available to users in the San Francisco Bay area, Fresno, California and the Boston area. Yet, Google does not hide its ambitions to extend it globally.

Google describes the online tool, named “Project Sunroof”, as an attempt to create a “treasure map” for solar energy, essentially adding solar data to its Google Earth aerial mapping to identify areas with the best potential for solar generation.

The tool estimates whether a home’s rooftop is suitable for solar power generation, what the installation of solar panels would cost, and what could be the homeowner’s savings from monthly utility bills.


As a general rule, online solar audits in Europe are available on a local, that is to say country-wide, level and are offered mainly by installers as free service on their websites. The UK was until recently very attractive solar residential market and a number of installers like SolarWorld UKoffered basic online calculators.

France will also shine more brightly on the online solar audits map from November. A start-up company with the self-explanatory title In sun we trust” will launch an online calculator to help French homeowners decide on going solar.

Just by knowing your postal address, the tool will combine geographic data with solar radiation map, find the applicable feed-in tariff with French utility EDF SA (EPA:EDF) and voila, you have your solar audit ready. The site will also offer a list of nearby installers who can actually deliver the panels and fit them on the roof.

In sun we trust will primarily work with local firms but any company on their list will have to meet a number of criteria, including certification, labelling and training as well as professional experience and number of installations in the past year, founder David Callegari says.

AND WHAT ABOUT EMERGING MARKETS was launched this August to specifically target solar power opportunities in emerging markets. “We provide to businesses in emerging markets what Google’s project sunroof provides to residential users in the United States,” the website says.

To get your free solar power audit delivered to your mailbox, you have to complete a survey and upload required data on the prospective solar power site. The solar audit you receive will contain data on the solar potential of your site as well as the type of solar technology and equipment best suited to maximize the solar energy output.

The company sponsoring the website may offer you solar purchase, loan and lease proposals as well.


It looks so sweet, right? It’s easy, it’s online and it doesn’t cost a thing.

Reality is a bit less sweet.

Online solar audits have limited value. They can show you the big picture but every additional factor that gets added in the calculator can dramatically change its accuracy.

Shading analysis, for example, is crucial, for making the most of your solar power plant. Since solar panels are usually connected in strings, a single shade on a single panel can adversely affect the output of the entire string.

Trees, antennas, chimneys, electricity poles, thick power lines, raised roof sections and even consistent steam all need to be factored in and only on-site analysis by a professional can best identify possible obstacles and how to go about them.

In many cases it’s going to be far more effective to get a qualified solar installer to review your details and come up with a hard cost estimate, payback period and benefits.

Yet, if you are serious about going solar, online is still a good place to start, if only to educate yourself on how to best pick your installer.