With energy prices on the rise and awareness of climate change growing, interest in solar power has been increasing among private homeowners.

But with variables from weather patterns to roof angle impacting effectiveness, only certain homes are suitable for adoption of solar technology. Now, at the click of a button, residents of the District of North Vancouver can find out if theirs is one of them.

Early last summer, the municipality launched an application on its website called, simply, "Solar" that allows users to locate their home on an online map and view a diagram showing how much sunlight hits each square metre of its roof over the course of an average year. It indicates which precise spot would be best for the installation of a solar hot water heating system, and assigns the whole surface a rating from poor to excellent in terms of its overall suitability.

Users whose roofs appear to be good candidates can then punch in some additional information about themselves -- how many people live in their home, whether they use gas or electric heating -- and the program will calculate how much money, if any, a solar heating system added to their existing setup would save them on their bill.

"I think it's just a way of informing people of what their options are," said UBC graduate student Rory Tooke, who helped develop the project. "We tend to be talking a lot about renewable energy technologies, but I think people still don't see the real numbers in front of them."

The tool was created using Light Detection and Ranging, or LiDAR, which uses laser light to gauge the distance between objects. In 2007, when the district was preparing to take aerial images of the municipality for mapping purposes, it chose to equip the plane with LiDAR as well. As the aircraft flew over the community, the device shot millions of pulses of laser light at the surface, timed how long each took to bounce back, and used that information to determine the precise distance between the plane and the point off which the light was reflected.

The result was a three- dimensional image of the entire community, which included details down to the shape of individual trees.

When UBC's Tooke and his supervisor, Nicholas Coops, heard the district had done this, they approached the municipality and asked to use their data for a larger project they were working on on urban energy generation. In return, they would give the district the map they created from it.

Tooke ran the numbers through a computer model that took into account the slope of individual roofs, their orientation, the location and height of trees and buildings, the movements of the sun, patterns of cloud cover and so on. The result was a map that showed the amount of sunlight that should hit every square metre of every home in the community.

Municipal staff took that map and built the application around it to allow users to zero in on their own home and work out how much they could save. A surprising number of houses turned out to be suitable for conversion.

"(The district) is lucky; we're situated on the slopes of a mountainside which happens to face south," said Shawn McLeod, section manager of the district's geographic information system department. "Believe it or not, the amount of direct and indirect solar radiation we receive in this latitude and in our particular geography is quite high."

The tool is apparently unprecedented in detail, said Tooke. Some other cities, including Boston and San Francisco, have similar applications, but they are much more rudimentary, taking into account only the height of buildings and assuming a static source of sunlight.

The tool has been featured in a couple of magazine articles, said McLeod, and it won a prize recently from the Union of B.C. Municipalities.

Now other B.C. communities -- Prince George, Kelowna and Richmond among them -- are interested in developing their own solar maps using North Vancouver's approach, added Tooke.

So how many North Vancouverites have actually used the application?

"That's a difficult to answer," said McLeod. "I think the usage is definitely increasing."

So far, at least five households have installed solar heating systems since the project began and have agreed to have their homes noted on the map. Another three are on the way, he said.

It would be good if more joined them, said McLeod, but he acknowledged that as a new technology, it will likely be slow to catch on. "It's not something that's going to spread like wildfire," he said.

To try out the district's Solar application, go to www.dnv.org, click on the GeoWeb link at the top right of the page and then select the "Solar" tab. The tool doesn't work on a Mac.

jweldon@nsnews.com